What is the difference between the John Deere 6R 120 and 6120E?

Here is how the John Deere 6R 120 and John Deere 6120E compare on John Deere's published specifications:

• Horsepower: John Deere 6R 120 118 hp vs John Deere 6120E 120 hp
• Pto horsepower: John Deere 6R 120 91 hp vs John Deere 6120E 102 hp
• Weight: John Deere 6R 120 14330 lb. vs John Deere 6120E 9410 lb.
• Fuel capacity: John Deere 6R 120 52.6 gal. vs John Deere 6120E 44.4 gal.