I would talk to someone in person who lives by you, like the person who quilts your quilts. I would ask them what they like about their machine and don't like about their machine. I would ask them if they could do it over again, what would they purchase instead of what they bought. I would ask them what is the most important features of their long arm machines to them? What do they like the best? What do they not use? Find out from them everything you can. They will love to tell you their opinion.
That is what I would do first. Then I would go from there. I would ask her if she thinks I should buy a used one since I'm only using it for myself or if I should buy new so I get the extra help from a dealer. I would pick her brain. She will be delighted that you think enough of her to ask her opinion and she will be completely honest with you.
Dealers want you to buy their machines. People selling their used machines want you to buy their used machine. Your long arm quilter is the one who has nothing to gain by talking to you. She'll even show you how her machine works and what she likes and doesn't like about it. Call her and make an appointment to talk to her for an hour. Please!