After looking at the specs again, the 670 is a wide body but much lower on power than the rotor wide bodies. Also, it does not offer the bigger, dual tank fuel capacity. Having said that, the walker will not consume as much power or use as much fuel.
Not much for activations, especially if you buy a used one that has been operated the way you would.
"Auto Pilot" doesn't mean much. Claas has had that for years and years. That can mean it cad do something as "basic" as the steering wands on a corn head that controls the hydraulic steering on the combine without any gps equipment or mapping. It can also mean more than that, just depends on how the combine is equipped. Most use Ag, Leader, Deere, or Trimble for the auto-steer on these machines. I like Ag Leader. If you already have some gps equipment that can be shared, that can help make your decision. I think the Deere can do everything the others can do, including steering on curves, not just A/B lines. If you want a more improved auto-steer, I think 2014 and newer Lexions have better hydraulic autosteer components than before.