There are several key differences between the John Deere 4520 and 4620 models. The first difference is that the 4520 has a Yanmar three-cylinder diesel engine with 48 horsepower, while the 4620 has a four-cylinder PowerTech diesel engine with 55 horsepower. The second difference is that the 4520 has twoWD/4WD options, while the 4620 only offers 4WD. Additionally, the 4520 has an open operator station, while the 4620 has a closed operator station. Finally, the4520 weighs in at 5,500 pounds and has a wheelbase of 92 inches, while the 4620 weighs 6,100 pounds and has a wheelbase of 102 inches.