Well from a research stand point most lower end mowers in the $3500-4500 range use the same zt 2800 hydro gear wheel motors..4500-7500 youll get zt 3400 or 10-11cc parker..most all offer same engine options of kawasaki,briggs and stratton, kohler, vanguard...ive been told by multiple professional landscapers to go carbuerated and mainly go kawasaki..tho most have hadgood luck with kohler too. Only real difference is design and how the fuel delivery is set up...ive heard alot of good about the hustlers,exmarks, and scags