Always gotta have atleast one flash in the bag. The flash was the first disc I actually started to get major d with and be able to throw dead straight. Although I haven't thrown a surge too much I'd say the flash is far superior. I might be a little biased, I think I got 5 or 6 aces with a flash and none with a surge :) In the wind though the flash does tend to suck and a surge wud probably be better
It depends on the disc and what you want from it. In the predator, I like Z because I want that thing to stay overstable longer, as Z is more durable. In the surge, I definately like the ESP version better. Better glide and straighter/longer. It held a line longer before fading off. I didn't like the Z surge at all.