I'm going to second and third the suggestions about going to a big show and driving every machine there. You may need to go to several shows.
Buying a longarm is like buying a car: What works best for each of us may not be what's best for you.
Start with the features:
I wouldn't be without the hydraulic lift and the ergo-handles, but them I'm quilting 5 to 8 hours a day. I need to be able to make small changes to save my back.
Do you want/need a stitch regulator? It does make that learning curve a little flatter.
Do you need a dealer right next to you, or are you capable (with a little training) of diving in and working on your own machine?
Good luck, and HAVE FUN!