The level of Superman's resistance to magic is based on his motivation. Motivated enough Supes would PWN any magic user...without real psychological motivation he'll get pwned versus serious magic.
Since nothing like that is mentioned, it looks more in Strangefate favour, apart from Strangefate being dumb and trying to use verbal spellcasting which easens things for Supermen a lot, but Strangefate with Infinity Gauntlet has all the ways to avoid being pwned and to kill Supermen in a horrible, horrible stomp.