Rhydon

Ouch!

If you are going to use it against Snorlax, then there is very little difference between the moves, once you consider Snorlax weakness to fighting.
I know, it doesn't compensate for such bad luck...but it puts a slightly more positive spin on it.

What do you want to use Rhydon for? He's not a good defender with his double weaknesses and for Attack his only use is against Snorlax and Blissey and even in those matchups there are better options like Machamp. If you need him because of multiple Snorlax then RS performs equaly to MS, so here your RS/E one is perfectely fine. There are comparison vids of the different movesets on youtube who show exactely that.

for some reason i prefer rhydon with rock smash / earthquake , over mud slap / earthquake
i use them as an attacker for snorlax and other rhydons
may be it is just a personal preference

Well, I don't know where you people find all of that Rhyhorn candy. It seems that everybody has Rhydons. I am only level 25, but still...I have only seen ONE Rhyhorn in the wild and have only hatched a couple from 5km eggs (5km eggs almost always give me rubbish). It annoys me, because I have a 100% IV Rhyhorn that I am itching to evolve. Just need more candy!

Anything but Megahorn...