Hello! One of our local Olimar mains has really been stepping it up recently, and I have some good notes I'd like to share.
I think the MU is near 50/50, could possibly be either side's favor by 5. R.O.B can kill Olimar much easier than the opposite, but Olimar can rack up damage much, much faster. Olimar's pikmin, as well with his good combo ability, ****s with us a lot.
I believe the prime range to be in will be either 1. As close to him as possible, probably ftilt / dtilt range. 2. Just out of the range of his pikmin toss. Most of the game will be played at range 2, but range 1 is where we have the biggest advantage.
Pikmin can grab the gyro, but it isn't necessarily a bad thing. The pikmin on the gyro are still a hitbox, and will damage you if you're holding the gyro or standing next to it. Even with a pikmin attached, the gyro is still R.O.Bs. Sometimes a pikmin will try to bring the gyro to olimar, and it will hit him. I've gyro spiked Olimar because of this.
Olimar doesn't have much to kill R.O.B besides rogue smash attacks and kill throws. If we make sure to not get grabbed we're set. Olimars Fsmash has less lag than you'd expect, so he can fsmash again to punish your punish. I think if he fsmashes our shield, we should have enough time to side b and reflect the next one. I'm not too sure, this is something I should check.
When there are pikmin on you, use Utilt. It's the best move for getting pikmin off you. Side B also works well, I think this is the only match up even worth using side b in. The reflecting aspect can really mess with olimars who aren;t expecting it, and the pikmin can extend the hitbox, to make it even more jank. I've had an olimar walk into the final hit and dying, because he though the move was over.