does rockslide still breathe oxygen? (IDK honestly someone please tell me)
I think clayface could erode rocks as well.
plus if you take his arm/legs off and toss them they don't automatically comeback like mjolnir.
there are certain clayface's that could duplicate powers too so IDK
I honestly don't think they can hurt each other conventionally by using there own powers. as they both can reconstitute themselves and are basically invulnerable. Though I would say clay is more invulnerable.
with prep I think clay will take it
new Orleans is Humid AF and below sea level so I believe there should be enough ambient moisture for clay to do what ever he wants. also there is plenty of granite everywhere for rock to reform himself as well.
I'd give Rock the majority on both locations IF he cannot be suffocated and if he cannot be eroded/corroded.