That's really nothing compared to what Magik can do. Magma is a planetary threat at her best. I'd argue she may even be an omega-level mutant if writers had more interest in her. But Magik is a dimensional-level threat. She is a hell lord. In Limbo she is practically god, and even on earth she's one of the most powerful sorcerers alive. She once absorbed the entirety of Limbo into her being. She has defeated Dormammu by herself and frightens the likes of Hela and Satannish. In her weakest form she's fought evenly with Thor multiple times. She's casually defeated and depowered Juggernaut multiple times. She's killed an entity called the 'world eater.' In any alternate timeline where she goes completely evil the entire X-Men are completely helpless against her. In one story Dr. Strange takes her to a dying dimension so she can vent excess power because in his own words destroying that dimension would be a mercy. Magma isn't close to being in the same league.
If you restrict the discussion only to their mutant powers then Magma can be considered the most powerful, specifically if Magik's potential for time manipulation is discounted. But when taking all of her abilities into account, Magik operates on an entirely different level from Magma or any of the New Mutants.