Even is what I'd guess as well. Though I can't really tell since I've always had trouble fighting Yoshi with whatever character I use.
Speed is regardless Shulk's best punish option against Yoshi, since we can (as mentioned above) punish Egg Toss and we can land a grab here and there. I also like pulling a privot Ftilt when
Speed is active. Even at high damage,
Shield shouldn't be recommended, as I have experience with Yoshi's combo-power, and if they get us offstage it's probably over. That leaves
Jump and
Buster to rack-up damage.
Jump is pretty good to avoid camping shenanigans.
I think the reason I have trouble with Yoshi is because I have trouble actual K.O.'ing him. That's where
Smash comes into play, and I am able to K.O. on a much lower percent. Although we have to be careful (we as in
) since it makes it much easier for us to be K.O.'d as well, and either UpSmash or Fsmash would be enough at around 80% (with
Smash active).