Thor's hammer control over magnetism is at least on par with Magneto's.
Yes...magneto may get lucky if this Thor's not taking him seriously.
Outside of Ultimate thor (when he wasn't like he is now), magneto couldn't control mjolnir.....certainly can't take it out of thor's hand forcefully or make thor bend to his power like the old Ultimate thor......thus Thor is a decent landslide
If thor brings a full force storm or godblast, or just amps his hammer, or absorbs mags power....any of these aren't auto wins...but they sure give thor a most massive edge....
Magneto and Thor against the Surfer and Terrax!
I say Magneto and Thor take it in a landslide victory.