i saw it recommdened to get 4WD if you have any variations in terrain - rough ground, steep slopes, wet areas. i'm glad i listened to that advice, the 4WD has made a tremendous difference in mowing. and it's already come in handy for pulling trees too. had zero plans for that, but worked great.
doesn't make sense, but mine doesn't really seem to slow the tractor down anything noticeable by having it in 4WD verses 2WD, which is why i guess so many people just say they leave it in 4WD all the time as long as they aren't on hard surfaces/pavement.
if yours is completely flat, then sorry to bore you!
if you don't get any responses you can probably look up the PTO hp requirement for the equipment you want, since you know exactly what it is, and see what kind of PTO hp the tractors have that you're looking.
good luck!