I'm surprised that you haven't found several threads on this site about purchasing long arms. Yes, do go to a major show and try all of them. Also check the LongArm University website for a checklist of features for you to consider. You mention that you and your wife will both be using? You'll need hydraulics to adjust the frame/table easily as they are super heavy. Also, you don't say, but you might be interested in a computerized system if you plan to start a business.
Any brands (Innova, Gammill, APQS, Nolting, etc) that is a true industrial machine will last forever, so don't shy away from purchasing used.