You ladies have covered about all the bases, but I will add a couple of ideas ... YouTube BerninaJeff, he is a whiz with all things Bernina!
I have the 440QE and like several others think that the 5.5mm feed dogs are better for quilt piecing. I just became aware that there is a model that is made for the European market but can be special ordered here in the US. The B720 has 5.5mm, 10" throat, jumbo bobbin, and thread cutter. All features that make it an attractive choice for piecing.