A bit late to chip in but oh well
I have VT80 in 4U G5 and ZS 3U G3 both with BG66UM @ 26lbs and I play doubles & singles. I bought the VT80 first and I loved it at the start...it is very easy to generate powerful smashes consistently and net shots are easy. But then I used my brother's ZS and knew I'd be buying one almost immediately. When you hit the sweet spot
YOU WILL KNOW, and so will your opponent(s)! The feeling is addictive, but because of the smaller racquet head it means you have to be very consistent which seems to put off a lot of people. The ZS also feels less stiff than VT80. I think that I am more of a wrist player, so I can pull of the shots that I want a lot easier and with less effort with the ZS.
I've had the ZS for about 4 months and now that I've adjusted to the smaller frame, my VT80 is gathering dust. I've also tried my friends 3U VT80 but I find it doesn't match my play style as well as the ZS. However, I recently bought a MX80 and I've found that it destroys both of these racquets when it comes to defensive play and drives. But in the end I still keep on coming back to the ZS, although VT80 is still very good if you like stiff head heavy racquets.