Oh boy, you are going to get as many different answers as people here. I have a Janome 6600P and here's how I made my decision...
Explore some features that are available.
Make a list of features that you really want.
Make a list of criteria that is immovable - for instance, price.
Make a pile of fabric and batting sets.
Take your fabric samples with you and USE as many machines as possible. Keep notes on your impressions of machines. Shop owners do not mind if you come back more than once. They also appreciate that you are doing some serious shopping and know that every individual will have preferences. Of course, they hope you will come back to them!
As I did this, I learned about new features and was able to choose what I wanted. Another thing I did was to talk to the serviceman in as many places as possible (actually my DH did much of that for me).
If this sounds like a lot of work, well, a good sewing machine is worth every bit of it.