I have all 3, and it depends on the application which I prefer. The VIPER HS is a great load development/target scope, inexpensive, fine reticle (2 fine to hunt with for me) and OK glass.
ZEISS Conquest, I use for large game hunt's.(heavy reticles)
LEUPOLD, best of the "hunting/target" combo glass.
BUT, everyone's eyes are different, so check them all out first, then buy the ones that fit YOU best.