>>2728546If they outright fought, Dagoth Ur claps Sephiroth easy.
But Dagoth Ur would still probably die if Meteor struck and obliterated Nirn, and would probably be vulnerable to Jenova mind fuckery, especially since she preys on delusions most of all.
Honestly, I actually lean Sephiroth. Dagoth Ur is too prideful to take the threat posed by Meteor and Jenova seriously, and is liable to just let Sephiroth do as he pleases, which, while weaker overall, Sephiroth has one VERY good trick. If he took them seriously, Sephiroth would have no chance, but I doubt he would.