Blaargh. I'd like to say Mario has an advantage here, maybe even depending on counterpicks. Link's spam game is difficult to deal with, our Cape can't stop everything. Your z-air outranges, and outprioritizes all of our moves.
However we have the tools to gimp you easily with a well placed Cape, B-air, FLUDD etc. You'll want to have extremely good DI, so you don't put yourself in such a bad position to get gimped. However Mario's recovery isn't the best either so a well placed z-air edgehog can gimp us, are maybe even a n-air? If you time z-air wrong however you can get stage spiked at battlefield, which will K.O you instead.
Mario can combo Link quite well at low %'s due to Link's weight. We can most likely get 30-50% damage at most with a well placed utilt, dthrow combo.
Mario and Link have about the same K.O moves, you have fsmash, d-air, and dsmash. We have fsmash, dsmash (it can send Link in a bad trajectory to get gimped), and usmash (with good DI on the Link, I can see this being a hard move to K.O Link with.) If Mario is offstage, and up B's chances are you can hit him with a d-air, and easily K.O him. Mario has fsmash which has good range, but is kinda easy to see coming

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IMO I'd go with 55:45 in Mario's favour or 50:50.