I played HugS in this match this weekend and it was fairly even...I beat him on Dreamland, he 2 stocked me on stadium, and I 2 stocked him on FD.
I think Samus vs. Peach is pretty even, but ultimately Peach has the upper hand, but it's not unwinnable for Samus.
First Peach can eat missiles with virtually every move. Slaps, dash attacks, smashes, nairs/bairs, everything. That's kind of a major problem for samus because it removes her main way of approach and across the stage pressure/sheild drain. I think a well timed bair can eat a fully charged charge shot as well, but I haven't tested this in a while.
Secondly, downsmash takes away one of Samus' main strats of CCing, which severely hampers her game, whereas Peach retains her CC ability.
Third...I think Peach has easier kills. Outside of a gunpunch or downsmash, I think it's much easier to fair samus off the level and just throw turnips at her bombs than for samus to land a kill on peach (which outside of the 2 smashes I mentioned is probably going to be a nair or bair.)
To really screw up peach, samus should have impeccable spacing to avoid fc approaches and retaliate with fsmash/downsmash. Screw attack out of shield is also really annoying, as well as not dying. Just take advantage of Peach's weaknesses and try not to recover so predictably.