I said it was a disadvantage, 40-60, lol. It used to be one of Olimar's worst MU's along with MK, Weegee, and Falco, but it's gotten better since then.
Olimar is infamous for camping. At the most basic, he simply:
-throws pikmin to accumulate damage
-alternates fsmash/grab (combos at low %) to space
Now, for Olimar's main flaws, and Peach takes advantage of every one:
-OLIMAR'S MAIN PROBLEM IS LACK OF PRIORITY! Yes, it's more of a problem than his recovery. Olimar's pikmin have hurtboxes, meaning Peach's high-priority aerials are very safe to use against him. Actually, nearly everything out-prioritizes him. But anyway, Nair and Bair are quick, safe, and get rid of Pikmin against Oli. Peach's Dair is terrific for approaching (if used correctly, or it can otherwise be Usmashed Oos).
-YOU MUST RECOVER! No, Olimar sucks at recovering. Because Oli uses a tether recovery, Peach can edge-hog him infinitely when he goes offstage. Peach is already terrific at edge-guarding, but if Olimar tethers a ledge, and a character is edge-hogging, it will knock the character off the ledge, BUT IT WON'T GRAB ON! Meaning Oli falls and dies.
-Olimar's grab runs along the ground: meaning Peach can safely approach Olimar, pressuring Oli with continous, head-on aerials.
-Olimar's Fastest Move Takes 4 Frames : Peach's Jab is only 2 Frames: Peach will jab at Olimar every chance she gets to. Oli has nearly no safe options (if not none at all) to defend against her jab > grab/jab 2.
Edit: Wow I wasted a lot of time on that.