so you guys believe they are absolute equals even by feats?
Mu is slightly more powerful but they're both high kage level and practically on par with each other.
can the clam be located only by contact sensing?
Yeah, they tie. There's no scenario possible where either one could win against each other unless we restrict the mirage genjutsu. To be honest this is another point against that whole "outlast the clam's time limit" argument... If Gengetsu managed to keep that genjutsu up for so long that both he and Mu lost a lot of chakra then clearly "outlasting" the clam isn't going to be viable for most shinobi unless he/she has absurd amounts of chakra like Kisame or the Raikages.
Mu isn't know to have high chakra levels tho. Absurd claim.