The H55 is very much one of the more 'budget' AIO from Corsair (although respectable temps can be achieved), whereas you're definitely paying for the aesthetics of the V8 GTS - not necessarily it's 'cooling ability'.
Review of V8 GTS: http://www.hardwaresecrets.com/cooler-master-v8-gts-cpu-cooler-review/8/
I'd say the H55 is better at actually 'cooling' in most scenarios, whereas the V8 GTS looks better.
Personally, I'd recommend neither. I'd suggest you look to a Cryorig H7 over either of them, and it's actually cheaper than both too!
http://pcpartpicker.com/product/93Crxr/cryorig-cpu-cooler-h7