I own 2 Brother and 3 Janome embroidery machines and here are my thoughts. I actually like the Janome hooping system better than Brother. The hoops are easier to attach to the machine, and the carriage arm being on the right doesn't make hooping a quilt harder. In fact, not having the arm underneath the bulk of the quilt like it would be if the arm was on the left is better I think. The Janome 500e and the 400e both have a large color screen, and I find the Janomes are easier to operate than Brother machines. The 500e has an 8x11" max embroidery field where the 400e has a max 8x8, that's the only difference between the two machines, with about a $500 price difference. They both have a very large extension table too, which is another plus.
I'd stay away from the Singer machine, it's not getting very good reviews.
Cari