For a homeowner, I always recommend a wheel machine over tracks. Tracks are awesome but come with a price if the machine isnt making you any money. When they wear out its a $4K bill, not to mention and undercarriage costs associated. But bobcat does make a good undercarriage. Stay away from a Cat whatever you do. They are stupid expensive to repair, plus hand controls are in any machine, are expensive and almost impossible to fix on your own. When Bobcat switched from Kubota to Doosan engines, a few years ago, the Doosan engines came with fuel problems that are supposedly ironed out. I dont know exactly which year the engine swap was, but I'd stay away from the first model year or two that occured. A S650 could fall into that year, so check to see which year the swap happened. The serial number plate on a 650 would have the manufacturer year stamped on it. If your going to run any attachments, you may want a machine that has decent aux hydraulic output, not necessarily high flow