The XL 260 is 1.5 tons heavier than the standard 200, but comes with 2 more heat sinks in the engine. It is also the largest engine that will fit in the AL. However I imagine that is not the answer you are really looking for, since the XL sabotages the "zombie" ability of the Centurion class. But that's part of what I say by "if you don't mind being so slow." Personally, while I was mastering them, I put a standard 250 in and worked with a "bralwer" set up featuring 2 SRM6s, 3 medium lasers, and a TAG, then 2 Streak SRM 2 and 3 medium pulse lasers for a while, before ECM was implemented.
I do have a thing for TAG, but that might be a better topic for a different post. But part of that is the fact that it is really hard to actually use 4 or more energy weapons efficiently except for small lasers.
Here is the rub. Medium lasers generate 4 heat per shot every 4 seconds. Large lasers generate 7 heat per shot every 4.25 seconds (1 second duration + 3 or 3.25s recharge). With a standard heat sink cooling at 1 heat every 10 seconds, it is going to take 10 per medium laser, or 16.5 per large laser to stay perfectly cool. 2 mediums + 2 large and you really need 57 standard heat sinks, or about 34 double heat sinks to be able to use it all 100%. That's more than will actually fit in the chasis, let alone in a mere 50 tons. 15 doubles will get you about 38% of the cooling you need to fire constantly.
From a DPS perspective, you are going to be overheating quickly if you fire all four lasers. You are better off using 1 large and the 2 mediums instead of everything. Alternatively, you can just use the 2 large lasers and wait to use the medium lasers until the arm falls off. At range, using the LRM 10 with a single large laser will get you a better DPS simply from the fact that the LRMs are more heat efficient.
There is a counter argument that suggests that doing a lot of alpha strike damage is good in engagements where mechs are constantly popping in and out of cover. But the way I like to build my own machines, I would be more than happy to drop one of the large lasers for a TAG, extra ammo, and a bigger LRM launcher. Compare for yourself.
2 Large Laser LRM10 AL:
http://mwo.smurfy-ne...ed0a53667e5a1ac
1 LL, TAG, and more missiles:
http://mwo.smurfy-ne...bf4a55fdc2e9933