I'd rather Square Enix, to be honest. I'm not even much of a fan of THQ's games, but the way Square handled the Eidos acquisition just about sets the standard for how big companies should absorb one another. No meddling, financial support, sharing of tech/development know-how, etc.
ZeniMax might not be so bad, but Square essentially lets Eidos run as they had before the acquisition. I can't think of a much better way to do things than that, although in THQ's case that might now be good for either party.