The 25 series in USA only have the A2000 2.0 liter 4 cylinder at this time. The larger 47 and 55 HP 20 series have the A2300T 2.3L turbo 4 cyl engines. There was some talk about the 25 series having a heavier gauge steel frame, but that may have been an upgrade the newer 20 series get as well. Also the seats can be easily swapped out. The 25 series have adustible 3pt links on both arms, whereas the 20 series is adjustable only on one side. Other than that, for the 25 series the PTO/Hazard buttons are on the fender, not the steering console like the 20 series. Oh, and the chrome pieces on the hood for 25 series.