What is the difference between the John Deere S170 and S180?

Here is how the John Deere S170 and John Deere S180 compare on John Deere's published specifications:

• Wheelbase: John Deere S170 48.9 in. vs John Deere S180 48.9 in.
• Cutting width: John Deere S170 48 in. vs John Deere S180 54 in.