I'm a big fan of GPU render engines, my main render engines are iRay and Arion, in fact the second one is the first one becuase it has a pretty neat production toolset... But... That said...
Men... Corona is the best and faster render engine I faced in my life, it can lack a few features because it's in development but anyways, so far, is the best render engine, the fastest and the one that gives me the better quality.
BTW it is now my main production render engine of course!
I would like to know the render times for Furryball in that computer, you can't compare CPU render engines like mental and vray in an OLD fashioned i7-930 with a GPU render engine using a Titan, one of the most modern GPU's in the market... It's a bit biased... Also the mental ray one is very bad configured... I'm sure of that...
Ericspl, what is your CPU?
Cheers.