Faster denotes velocity
Quicker denotes time.
I'll take quick over fast (as it suits my needs better as they stand today) but damn, that ZR1 sound is sex! The GTR sound is sterile in comparison.
It may depend on how many cars you have/want/can afford/project in your stable. If I had to pick a dedicated track car amongst the pair, it would be the ZR-1. If I need a track car to also do street and winter duty, then it would be the GTR.