Not sure if this is a simple enough question, but this is the only place I could think of asking this?
With perpetual rain no longer available, what are the key differences between Vaporeon and Jellicent? I know Vaporeon's got Wish support and Jellicent's got spin blocking and a more reliable burn in WoW, but are there a significant number of Pokemon that Vaporeon can cover with its higher base HP and SpA compared to Jellicent? Or will Damp Rock Politoed still be enough to have Hydration Vaporeon running around?
Simple enough, we think.
Apart from the typing and the other things you have mentioned, Baton Pass teams still enjoy the presence of Varporeon because it is an easy pass in a Heatran (after Pokebank) nad because it has Baton Pass of its own. If you are remotely interested in Doubles, they both are fine Trick Room tanks. Jellicent doubles as an offensive TR setter and a faster one can nuke both opponents with Water Spout while Vaporeon has a few support options like Helping Hand and the superior Protect, Detect. Also, in the more fast-paced Doubles where weather changes are far more common, five turns of rain is actually long enough to pull off a well timed Hydration Rest.
We wouldn't recommend you to run a Hydration Wall in Singles, although your mileage may vary. Tyranitar and Hippodown don't suck, so expect to see them a lot even after the weather nerf and the Wall needs more staying power. The Hydration Tank is probably a bit better because it deals huge damage to the other weather setters and scares them away. A way to pull it off is like Rest-Roserade: When you expect to run low on HP, Rest. When the opponent predicted that and changes the weather, switch it out and bring it in at another time when the weather is favorable. As a bonus, you are immune to other status during that turn.