As is, it's clearly better because it's continuous CC. Either way, make the upped HP odd whether it's Gravity or Earth.
Why not Earth? Because Earth doesn't have the highest hp creatures, and crushing something with weight has nothing to do with Earth. Being able to kill a monster doesn't fit Earth at all, with Warden only able to damage half the creatures you encounter in the game after being buffed, Basilisk Blood being a delayer, and Auburn Nymph being a delayer. The only synergy Earth has is that you can increase the HP (make it survive easier?) so that it can kill better (wait, what?).
Why Gravity? Flying Weight has synergy with Otyugh (and momentum).