Speaking as someone who doesn't own a LA, but has done a BUNCH of research into them, I think for myself I'd be tempted to go back to the dealer and what is their absolute bottom dollar because you've found another machine for sale privately that has Tru Stitch, but you'd rather buy from the dealer and see what he/she comes back with.
If you can get the dealer down $500.00 to $4200.00 (or even less!) that's going to mean you have back-up and peace of mind, plus you don't have to drive all that way and it would be worth the extra $500.00 to me.
Just some thoughts.
Watson