A lot depends also on your budget. How much $$ you have available to spend. You can almost never go wrong with a Bernina, or many of the older machines. Most parts are available for them and a far cheaper than working on the newer machines. I have an older Bernina 830 from the 80's I bought on ebay from a one owner. She was losing her vision and couldn't sew anymore. Best buy I ever made. I've never had to take it in for service. It will sew through anything.
Best thing is not to be in a big hurry and test drive a few to see what you like best. You'll know what is right for you when you find it.
I also bought an Elna Su model 68, again from ebay. It appeared to be in pristine condition. When I got it, it would only sew a straight stitch. Took it in for service and $35.00 later it is like a new one. The original owner never used it and it just sort of froze up inside. Now it works perfectly.
Good luck to you with your decision. Everyone needs a backup.