Cheaper, better, and its the way you want it. Not having to change out half the system when you get it. There's no such thing as problem free. Im in the middle of building a new pc, but im doing custom shit like custom watercooling with modded pc case, custom built and designed radiators, im now looking at building my own psu shroud because the company that i was going to get do it wont ship to australia. Also modding a 5.25" dual bay reservoir into my psu shroud, plus trying to make everything fit is a big challenge. Could of just bought an aio, but won't get as good as a result with cooling.