I have a new 535 (picked up in April) and love it. I was able to try out a 770 for a good amount of time 25hours+ with my own projects and came to the conclusion I didn’t like the 9mm feed dog even with the dual feed but really liked the 5mm. The big thing lacking on the 535 are the nice embroidery features of the 590/790+ which would be really nice to have but for me 5mm feed dogs is a must feature so bernina has few options for me to be looking at.
if I get in to embroidery enough that th lacking features are a giant pain it is most likely time to be looking at a better embroidery machine anyways.
so if look I would write a list of must, would like and features to tryout in order to find your best compromise which maybe a bernina or not.