Unfortunately, most of the mechs and variants in the game are currently useless due to PGI's inept balancing, so this choice is not as obvious as it would seem. It's not a simple matter of going "Oh, this mech looks like it has good hardpoints, i will take it!". Nope.
First thing's first : Take a look at the mech lab options in this forum, there is an online one and a downloadable one. Modifying a mech in them is much faster than trying to do the same ingame, even if you have the mech and all components purchased.
The current metagame heavily favors two things : ballistic boating and sniping, preferably with jump jets. Any mech that cannot do this is by default, at a disadvantage (exceptions : fast mechs that can cap, and ECM capable mechs). Don't expect this to be fixed any time soon, this has been broken for more than 6 months and PGI refuses to fix it. The most terrifying mech to encounter in this game is not an Atlas....but a jagermech ballistic boat that will shred an atlas in no time at all (due to PGI's amazing weapon balancing).
This guide is intended to help you examine a mech for the not so obvious things that will make a difference ingame when you are using it. I'm not going to talk about things like play style or looks or faction allegiance, etc.
Mech Tonnage
Mech tonnage is, in theory, important because it determines how powerful your mech can be (roughly) in it's weight class. The current matchmaking system will attempt to match two teams of equal weight classes against each other (which it frequently fails to do because PGI is bad at making things work). Taking a 20 ton Locust that will let your enemy have a 35 ton Jenner is not a good idea, which is part of the reason why people don't favor the lighter mechs in each weight class.
Mech Size
This is hard to tell, because there is no way ingame to compare mech sizes against each other, short of dropping into a match and comparing it to friendlies. This may seem obvious, but larger mechs are easier to hit, especially with spread weapons like LRMs, SRMs and the LBX. This is also why some mechs are simply terrible, even though they have decent specs on paper....their size pulls them down. A 40 ton Cicada is meant to measure up against other lights, but it is MUCH larger (and hence, much easier to kill) compared to the 35 ton Jenner. The Atlas is also not used much (barring the ECM version) because it is a HUGE target. You want to pick a mech that is correctly sized for its weight class, and isn't overly large. Larger mechs will draw much more firepower on the battlefield due to human psychology, nobody wants to try hitting a Kintaro going 100 kph when theres a big fat Atlas next to it.
Example of mechs that are badly oversized : The Atlas, Awesome, Cicada, Quickdraw.
Scaling chart courtesy of Kong Interstellar. I make no claim to the accuracy of this chart :
Hardpoints
This is really, really important because while some mechs have great hardpoints on paper, the location completely ruins them. PGI has so far refused to fix any mechs afflicted with hardpoint location issues for more than 1.5 years since closed beta started, so don't expect any fixes here, ever.
As an example, consider the AS7-D. 4 energy hardpoints, 2 ballistic hardpoints and 2 missle hardpoints, on a 100 ton mech. Should be able to fit lots of firepower into it right? But here are the problems with it :
-2 of the energy hardpoints are in the CT (only 2 free slots), which limits them to 2 med lasers basically.
-The remainign two energy hardpoints are located in the arms, which have useless arm actuators in them that do nothing but stop you from mounting more stuff in there, like heatsinks.
-Both ballistic hardpoints are in the same side torso....most ballistics take up lots of slots, so you cant really take advantage of both hardpoints.
-The max missle tube size is 6 and 10, which prevents you from using LRMs effectively. (See below)
In comparison, the Jagermech can mount 2 AC20s or 4 low caliber ACs. That is a lot more firepower than a AS7-D can put out, despite a 35 ton advantage. All because of hardpoint locations. Which is one key reason why you don't see people using the AS7-D much.
You also want to avoid mechs where most or all of their firepower is concentrated on one side. The HBK-4G is the best example of this. Take out the huge RT, with the very easy to shoot at hunch, and the hunchback is left with two lasers. This also includes mechs where their main weaponry is located on a very easy to shoot off arm, like the Yen lo wang. Large sized target, low armor, AC20 with only two med lasers as a backup, recipie for disaster.
Missle tube size
Missle tube size is really important because you want as many missles to be fired at the same time as possible. A LRM 20 fired from a 5 shot tube is 4 times as easy to take down via AMS. A SRM-6 fired from a 2 shot tube takes 3 times as long to fire, which can easily cause you to miss the follow up shots. If you are planning to use a mech with missles, make sure that all your missles can be fired at once.
Warning! Missle tube size is NOT showed when viewing a mech for purchase. This is why using a mechlab is critical. This is one of the things that PGI refuses to add into the client for some reason.
Weapon firing positions
The firing positions of hardpoints also make a big difference. The jagermech's weapons are mounted in the arms....which allows a very large range of aiming. You can stand on a cliff edge and fire at a steep angle while the enemies below are unable to hit you with their torso mounted weapons because they can't aim high enough.
The low mounted weapons on an Atlas, combined with the height of the mech, allows enemies to shoot you while you are unable to fire back....because your weapons are blocked by terrain.
Here's an example :
This happens a LOT in an Atlas. A jagermech could hide behind that rock, and snipe over it with his high mounted weapons....and your low mounted weapons wouldnt be able to hit him! Another fine example of PGI balancing.
Another fine example : The HBK-4G with 3 ballistic hardpoints....in the same shoulder....on a 50 ton mech....what are you supposed to put there, 3 machine guns? 3 AC2s? This question was asked a LOT in the beta and PGI refused to answer. Which is why you don't see competitive use of the HBK-4G.
Size of the CT
Most players are going to aim at your CT. Coring it is often the fastest way to kill a mech, and it is conveniently the largest target. The problem is that on some mechs, the CT is xbox huge.
Take a look at the Dragon :
The Dragon was one of the first mechs in the beta and it's huge CT, combined with nonsensical hardpoints, made it very unpopular. It was and still is one of the easiest mechs to kill. Nowadays the only dragons you see are often trial dragons, or people grinding c-bills in a hero variant.
Other mechs with huge CTs : The Catapault and Stalker.
Cockpit location
This normally would not matter as the poor netcode, lack of any working lag compensation in a 2013-2014 online game and hit registration bugs pretty much guarantee that nobody will be able to hit your cockpit anyway. The other day i had to kill a tker who was standing still 50 meters away from me slowly stripping my weapons off...it took more than 18 med lasers aimed at his cockpit to headshot him, because most of my damage was mysteriously going to all three torso locations and not just his cockpit. This problem has existed since closed beta, 1.5 years ago, when testers noticed that they couldnt accurately hit cockpits of AFK mechs. I wouldn't expect a fix at this point.
Location of the cockpit is important for two things : Blinding by weapons fire and cockpit shake. Let's look at a mech where the cockpit is conveniently located smack dab in the CT, the catapault.
As you can see, any shots aimed at the CT will inevitably splash onto the cockpit. Even if there is no damage to the cockpit itself, the pilot will be blinded by the weapons fire and he will experience a ton of cockpit shake. Trying to shoot in a mech like this while your screen is filled with black smoke from chain firing ACs combined with an earthquake simulator is not going to be effective. PGI never bothered to test this apparently.
Avoid all mechs with cockpits in their CT, at all costs.
Other mechs with CT cockpits : Atlas (most of the head is actually the CT and easy to hit) and Cataphract.
An example of how easy it is to blind certain mechs simply by shooting the CT (in this case, the Atlas) :
Jump Jets
Jump jets are important for mobility since your mech will get stuck on the smallest of obstacles without them, as well as being royally screwed in the canyon map. Unfortunately not all mechs can mount jump jets....and not all mechs have the same effective with JJs.
How JJs work is that every weight class has their own specific class of JJs. They generate different thrusts, and how heavy the mech is affects how far you can jump. What this means is that mechs at the upper end of a weight range are going to be penalized....a shadowhawk (55 tons) jumps a LOT less than a quickdraw (60 tons). Take this into account when choosing a mech with JJs. Li Song's mechlab is the only mechlab program i know of that includes JJ distance.
Max engine size
Aside from the fact that your engine size affects your speed, every 25 points of engine size gives you one additional engine slot for heat sinks. Unfortunately some mechs have very small engine limits. The BJ-1 is limited to a size 235, which not only limits it to the slow (for a 45 tonner) speed of 84 kph, but also prevents it from using a size 250 engine to get an extra engine heat sink. Conveniently, there is no way to see the max engine rating/speed ingame before buying a mech.
Keep in mind that you generally need to go very fast to be immune to most weapons fire, which requires a light mech. Going 100 kph in a medium still renders you easy to hit. This is part of the reason why fast heavies like the Dragon have very low survivability in MWO, compared to the TT.
Variants
You will probably find one variant that you like. The problem : the rest of the variants suck and you don't want to use them. The bigger problem : you are forced to in order to get elite efficiencies. It's going to be one painful grind, and that's something you need to take into account when picking a mech...you might want to choose another mech with better variants instead, but still similar to the loadout you are aiming for.
Edited by Jun Watarase, 08 May 2014 - 10:24 PM.