>>51742366>>51742192Most Max moves are stronger because of STAB boost, something Tera would only give to non-STAB moves (besides Fighting and Poison moves).
If you had a Thundurus with Wild Charge, buffed Fly (Fly but taking only 1 turn now for the sake of argument), and Foul Play, you would end up with 130 BP Max Lightning, 130 BP Max Airstream, and 130 BP Max Darkness. After STAB, that is basically 195 BP on Lighting and Airstream.
If you Terastallize Thundurus for Super STABs, they would only be effective 180 BP both, and Foul Play becomes 142.6 BP.
You can only choose 1 of these moves to boost too, you keep the drawbacks like recoil, and for majority of Max moves you are doing even more damage after the initial hit thanks to weathers/terrain/stat changes.
So while non-STAB Max moves are weaker than getting STAB, STAB Max moves (the most common Max Moves) are way stronger than Super STABs, with only a few edge case like with Hyper Beam or Fighting/Poison moves.