Well...this is kinda the Faction Play section of the board, so...
Anyway, it's been said elsewhere but the main difference between IS mechs and Clan mechs, aside from the particular strengths and weaknesses of their weapons, is that Clan mechs are for the most part optimized right out of the box with double heat sinks, CASE, endosteel/ferro-fibrous, and most importantly an XL engine locked at a certain size which gives you a consistent level of pod space to build your weapon payloads with. Plus a lot of Clan mechs have similar speeds with these locked XL engines so it's easy for them to reposition as a group and not have to worry about waiting on stragglers. IS mechs on the other hand are customisable in every way, and that seems like a good thing at first glance but it's much easier to bring a sub-par IS mech to both Faction Play and Quick Play because of all this supposed variety than it is to mess up a Clan mech.
So while there's this huge pool of possibility and creativity within which to build an IS mech (endosteel/ferro-fibrous or not? standard engine or XL?
what size?), only a small portion of that pool actually consists of mechs that can keep up with the Clans in terms of speed and firepower. It means the VAST majority of the time you need mechs that can move at least ~75 kph and can mount at least ~30-point alphas for dps builds or ~45-point alphas for up-front alpha builds with maxed or near-maxed armor. It means double heat sinks always, endosteel nearly always (and sometimes ferro-fibrous), and big XL engines the vast majority of the time. The Clans on the other hand don't even
have those other options because of how much of their loadouts they can't change.
So out of all the options available to IS mechs only a select portion of them are actually viable for faction play, whereas almost all the Clan mechs (except for the IICs and the Kodiak) come set up that way already and can only be altered so much. Newer players don't necessarily pick up on that right off the bat so they end up bringing nonviable builds to FP and getting farmed by all but the starchiest of Clan potatoes. Understanding that your options in the mechlab are restricted on the IS side goes a long way towards being competent in faction play, and being stuck with the IS XL engine means you have to know how to poke/trade and torso twist well if you don't want to go down early from taking a Clan alpha to a side torso. If you don't like those restrictions and that's what keeps you out of faction play, then that's a shame but I understand. But it's not like the Clans have wider choices than the IS does when it boils down to what's viable. While it's more difficult to bring bad Clan builds to faction play it's certainly possible and Clan PUGs get their share of stompings too.
Now, all that being said, once your IS mechs are optimized the way the Clan mechs come out of the box, you deal with the differences in the weapons. Clan weapons have more range and power for less tonnage but run hotter and have longer burn times and cooldowns. IS weapons generate less heat with shorter burn times and shorter cooldowns but they're heavier, do less damage per shot, and have shorter ranges (with one or two notable exceptions). It means the Clans do well when they can stay outside the IS's optimum ranges and trade with time to cool down, and IS tends to do well if they can force a brawl or if they can trade from within their optimum ranges.
The rest is strategy and tactics common between the IS and the Clans: balling up and pushing, forming firing lines, knowing where to go and what to do on the maps, and focusing fire.
Edited by The Errant, 02 February 2017 - 05:53 PM.