What is the difference between the John Deere 8RX 490 and 8RX 540?

Here is how the John Deere 8RX 490 and John Deere 8RX 540 compare on John Deere's published specifications:

• Weight: John Deere 8RX 490 50025 lb. vs John Deere 8RX 540 50025 lb.
• Wheelbase: John Deere 8RX 490 136.4 in. vs John Deere 8RX 540 136.4 in.