Olimar has little range in the air, putting him at a slight disadvantage. His Uair and Nair are the only things Mario has to really worry about. Mario isn't so strong if you stay under him. Mario does have the tools to win if he avoids the pikmin throw and can gimp effectively.Ahh Olimar, you know you love him. Now.
Olimar is a versatile character in the sense that he can be played extremely campy or extremely aggressively. Mario has to adapt to what the Olimar main is doing. Say the Olimar is playing campy, he will always be doing his Side B which is the Pikmin throw. Mario has been gifted with a cape. The cape CAN reflect the pikmin back at Oli and hit him with his own Pikmin. If you manage this, the Olimar will either start to sheild or do a Down B whistle.(In some cases, its just easier for the Olimar to kill his own Pikmin and then quickly pluck more.) This gets the Pikmin off of the Oli main and allows him to continue camping. What you'll want to do when playing against a CAMPLY Olimar is watch out for Olis insane grab range and Pikmin throw move. You can easily counter the Pikmin throw with teh cape, then approach with an aerial. Remember, he cant grab you if your in the air. This, however, brings up the fact of what if he sheilds my aerial? Well, chances are he'll go for Dsmash or an Usmash, perhaps a grab if hes looking to try and combo you. Both the Dsmash and Usmash come out pretty quickly but are incredibly easy to see coming. If he tries to smash you, sheild and then grab him. This opens up into Marios incredible Grab game which can get the Oli off the stage and set up for an easy gimp. Oli has a tether recovery, which is his biggest weakness. If you throw him off the stage, hit him with a Bair, and then cape him, hes toast.
Aggressive Oli is another beast, though. I will update this post after I use the restroom.
Purple Pikmin have little range, so it's not likely to call purple pikmin a real gamebreaker. The chances of Mario being in kill range, close enough for you to hit, be in a position where he can't do anything, and the you having a purple pikmin on hand are slim, slim enough to mean nothing in this match. Also keep in mind how small Olimar is, he'll die fairly early. Mario can "combo" pretty much any character, he has some amazing aerials. A majority of Olimar's game revolves around throwing pikmin, and with Nair and cape, Mario eliminates a key factor in Olimar's game. Mario can avoid grabs, seeing as how despite having good range, they're very slow. If he spotdodges, you'll be eating a dsmash.Well Hippo you really know how to steal the facts, also I find it is easier for people with many characters to just quickly grab the edge of the stage to gimp olimar. It does not take to much work to gimp olimar tether recovery. A good cp stage could really help win a match against a campy olimar. If you can keep track on what pikmin is up next for an attack that helps to. A blue pikmin means that the olimar is most likely planning for a grab, if you have high damage that blue pikmin can kill you with a back throw or heck an upthrow. If a purple pikmin is up for an attack, it can kill pretty soon with a up smash or down smash. Stages with low ceiling should not be picked in this match. Olimar can get in some good combos early in the match. I say 45-55 olimar's favor . Darn my grammar is bad.
The matchup is even at worst.