Well, Jellal has Darkness magic, as well as the OP speed-enhancing (as well as over-all OP) Heavenly Body, while Mystogan (while living in Earthland) has his staffs which allow him to reflect ranged attacks back at his opponents, cast strong illusions, generate beams of energy from the sky, along with a few other abilities. Counting in Mystogan's Mist Body technique to counter Jellal's close-range attacks, and Mystogan's Three Layered Mirror technique to counter most of Jellal's powerful Darkness, this match, IMO, ends in a draw...
While Mystogan has the ability to reflect back any ranged attack towards Jellal, Jellal has the speed to dodge any ranged attack Mystogan has with great ease (including Five Layered Magic Circle), though Mystogan has the power to avoid every single close-range attack Jellal can pull out. The only things that might tip the scales are Jellal's reaction time to Skyscraper (Mystogan's illusion spell) or Senma (Jellal's Heavenly Body spell which we know nothing about; all we know is he was going to use it on Jura of the 10 Wizard Saints to finish the battle quickly, and that Ultear and Melody had a freak-out when he began the spell).