Probably not Flyium Z, he has Ghostium Z Already. Also, isn't Bounce an event move? I'm not sure if he even has event Gyrados (VGC). (correct me if I'm wrong). He will probably not have Bounce Gyrados and will lack Flying STAB. Tbh, I'd use both in Battle Spot, *Brafnig* (Feraligator) is my boi, and isn't bad in Battle Spot, but Gyrados is a bit better (a lot if you have bounce). But I don't, and so doesn't most of Battle Spot, so I can see both as Viable options. If he has Bounce, use Gyrados+Power Herb. If not, it could go either way.