I would say that you would need the 24hp. I run a mowing crew that uses Walkers and basically collects everything all season long. I have the Billy Goat 23 hp loader and it works pretty well. Wet grass is the worst though. When the grass is wet I just have to slow down and not suck as much grass at any given moment. Basically it will suck large clumps of grass and you just have to wait for one clump to clear before ingesting the next clump or chunk of grass. If you dont, it will clog in the hose and pack itself in the blower housing. As far as leaves go, wet or dry it doesn't matter, my 23hp loader will suck them up all day long no problem. Straight grass with no leaves mixed in it is a whole different animal and much more difficult to suck up. Since I use my loader every day to suck up grass, I think I would actually like even more power. Since the one I have now gets the job done, I will just wait until the one I have now fails to upgrade to more power.