They all have strength/weaknesses to balance them out. I would pick different types to cover each other. charizard is the fastest of the originals, and has fly which gets stab in game it's relatively useful since opponents don't switch. bulbasaur had sleep powder, but other than that I didn't really like it's slowness, and weaknesses. I'm going with blastoise though for stab surf, and he can cover his grass weakness with ice beam, electric still a problem though.
I'm going with delphox I just found it gets dream eater, and hypnosis which are great ingame and for catching others. I don't really know about the new ones yet, but i'll trade after breeding some babies.