what type of terrain to you wheel in? in general terms, mud is going to put the most strain on a winch... nothing harder than trying to pull a rig buried to the frame in mud. For that kind of use, you'll want the biggest (highest # rating that is) winch you can afford. For not-so-muddy trail and/or rock use you could use a lighter winch and get away with it. Plenty of people use the warm 8274 of fullsize rigs, for example. Unless you do mud, I'd recomment something between that and the 9500# winches... oughta be enough.
j