Almighty Magic for me because it's Ultipotence without Ultipotence drawback (must have a clear enough idea of what they want to achieve and how they will do it. This double condition notably prevents the power from going awry and backfiring on the user.), with Almighty Magic you already have Indeterminacy and Metapotence as applications and you don't need any knowledge because Almighty Magic users do not possess that limitation, they are simply able to do as they feel. magic don't give a shit about logic & knowledge (hence Metapotence). anyway they both version of Omnipotence so they equal in power but different in flavor and how to do things.
Plus nothing prevent Ultipotence user from cheating and get Omniscience.
I imagine versus with ultipotence have an obvious patch where you can't just give yourself omniscience specifically because of that.
Other than that, I can't see any benefit one has over the other and almighty magic may just be magic ultipotence without magic weaknesses.