You want Rest as Politoed has no other form of recovery and you don't want your only Rain Setter to die as a Swift Swim team lives and dies on the Rain setters' survival. No idea why you would run Eject Button over Damp Rock. U-Turn does the same thing as Eject Button except you deal damage before switching out, and it isn't one time use.
Don't want to take over that person's post with this so I'll respond here.
1. Having the drizzler be the only one on the rain team that can cause rain would be foolish, so I typically expect it to survive 2 or 3 swap ins. Don't rely on it solely so It isn't that big a deal if it dies. Give rain dance to a starmie or another fast or durable pokemon like Kingdra.
2. I do 90% of my competitive battling on Pokemon Showdown and damp rock is banned on pokemon with Drizzle
3. The amount of damage a pelipper will do with U-Turn is insignificant. And 9 times out of 10 the pokemon it is facing will be faster than it and will get a hit off before the U-turn. That makes the U-turn pointless along with the small, small amount of damage it would do.
td;lr I try not to depend completely on my drizzler set up. Too much wasted effort would go into keeping it alive when you could just find ways to work around it with rain dancers.
Here's how I run my politoed:
(Politoed) (M) @ Eject Button
Ability: Drizzle
Shiny: Yes
EVs: 248 HP / 252 Def / 8 SpD
Bold Nature
IVs: 0 Atk
- Toxic
- Encore
- Scald
- Haze
If I came off as rude I didn't mean to.