I don't know... Extant is pretty powerful too.
This is very true. Extant is really just another version of Monarch, so it's really a question of which version is more powerful.
So if the question is Hank Hill's Monarch vs Captain Atom Monarch, I'm going with the CA version, since that's the one with the more impressive feats.
I'd like to hear what others have to say, since the Monarch vs Extant thread here on the Vine didn't really produce much of a definitive result.