What to do with my Rhydon's

Well, depends on stardust. I think first two are the best, MS/SE especially, since rock moves are now really good. I would definitely invest stardust in MS/SE one.

1 & 2. Lol I have a RS/Eq one and prefer my MS/SE much more.

TBH i dont like Rhydon. MS are slow, bad for dodging, and RS are a bit faster but no stab.
I am really happy with my RT/SE Golem at 2651CP. RT is very comfortable for dodging that i can kill easily my Snorlax 3075CP ZH/BS with 50% HP.
But lets say you WANT to power one of these Rhydons, i would go with MS/SE.

MS > RS

So 1st 2 are good.