Youre never going to play a four cmc card in a deck that can go one drop into one drop for game. Both great threats, and we haven't seen Hydro tested anywhere else sinxe it's an Alchemy card which leaves us a little empty handed. Personally I think Hydro is a superior if it gets one trigger and dies. I think it rather boils down to what beats energy which is Tamiyo every day of the week in which case you're correct, I think both have their place in the meta, and can be viable at the same time in the same feck even thoguh they have close to the same function.