I fought against Bo X7's Mario a couple months ago (friendlies, I barely won) and Bo partnered with Kirk, so it's not like he didn't know the Ike-Mario match-up.
If Mario is far enough to use fireballs safely, you have to approach him. There's no question about it, if you let him approach with the fireball you'll be in serious trouble if he gets through. If he screws up his spacing while using the fireball you can hit him with a retreating FAir, but don't expect to be able to follow-up well because you'll probably get hit by the fireball upon landing.
Mario has surprisingly nasty follow-ups when he gets a jab; jab -> grab -> DThrow can set up for some UTilt juggles if you get read properly, while BThrow/FThrow can set up for some edgeguards. Ike has the usual jab -> grab -> BThrow -> dash attack on Mario at certain percents, but Mario is the clear winner in terms of setups after a grab. If he does get in close enough to jab you, your best bet is to try and get away from him as soon as possible and keep him in between your own jab and FAir's range.
In terms of gimping, Mario wins. FLUDD destroys QD, but it doesn't really stop Aether if you make sure you sweetspot the edge the best you can; it will screw you over if you get hit with it on the way up though. Getting caped is very possible though; if you can, try Aether'ing onto the edge backwards so that if they do cape you, you can still grab it. It leaves you vulnerable for a free Smash attack though, so be prepared to DI. Edgehogging is still a good option for Mario if they want to play simple, or dropping down with a BAir. Ike cannot gimp Mario nearly as well; walk-off DAirs don't work well because of the massive hitbox that the Super Jump Punch has, so he can only rely on edgehogs. However, Ike can punish Mario more badly if Mario is forced to land on the stage with Aether than vice-versa with Aether, FAir, UAir, or DAir (if he's close enough).
In killing, Ike has the advantage as usual. Mario's only kill moves are FSmash (which can have some startling range if stutter-stepped), DSmash, and USmash, all of which are not so scary compared to other moves (except sweetspotted FSmash, that hurts). Mario is better at gimping; if you can mix up your recovery well enough to prevent him from doing that, it can be very difficult for him to kill you.
I'd say it's in Mario's favor, but not 40-60; more like 45:55.