Well, I suppose the inability to tote Yoshi from level to level does make things harder, but not by much; I mean, besides, assuming Yoshi(s) acts like he did in SMW (one hit, and it's a suicide run), I'd think skilled players deserve to be able to take advantage of his abilities--this could be one of those leveling-the-playing-field things, if anything. And besides, difficulty aside, it's automatically a step backwards because you could keep Yoshi in SMW, and losing him at the end of every level doesn't really make any sense anyway, realistically speaking.