What is the difference between the John Deere 6R 155 and 6MH 155?

Here is how the John Deere 6R 155 and John Deere 6MH 155 compare on John Deere's published specifications:

• Horsepower: John Deere 6R 155 153 hp vs John Deere 6MH 155 155 hp
• Pto horsepower: John Deere 6R 155 122 hp vs John Deere 6MH 155 120 hp
• Weight: John Deere 6R 155 17990 lb. vs John Deere 6MH 155 17637 lb.
• Fuel capacity: John Deere 6R 155 74 gal. vs John Deere 6MH 155 75.3 gal.
• Wheelbase: John Deere 6R 155 108.8 in. vs John Deere 6MH 155 108.9 in.