Pump fails... Warranty hassle
vs
Fan fails, go buy a new fan at your local store to hold you till better fans come in.
Seriously though with my Bitfenix Phenom I cannot see my Thermaltake NiC C4 tower cooler at all so it bothers me none really
Also like I said,
Fans are much much faster to replace than a pump on an AIO.
Another point is if it leaks (It has happened to some before) and you're out of a whole PC till you either buy the parts again or go through corsair warranty and inspects the cause of the leak and damage.