All three are super talented in their own ways and I think WWE is playing to each strengths perfectly right now. Reigns obviously sells because his size and power. Ambrose has the mic and ring physiology, and Seth has great in ring ability. Pairing him with Trips was the right choice out of the three.
I'd have to say out of all 3 though, Ambrose has the complete package. Can cut a great promo, never gives a bad match, and has a unique look to set him apart from the rest.