only reason why i am not sure on which one to choose is becuase the 90 is all copper which is nice, but the 120 can hold 120mm fans and will keep my comp quieter.
The XP-120 is around a degree higher load than the 90c, and is quieter (if you make it so). It also has a solid copper bottom that makes contact with the cip - just coated in nickel or whatever.
xp-90c is kinda harder to install than a 120, xp90c is alot heavier because its solid copper its something like 750grams, tho the xp-120 is alot bigger.