I have the Bernina 830 LE and so far have quilted one quilt with it on the frame. I was very pleased with the way it worked. The Bernina 820 would give you decorative stitches, the regulator and the ability to put it on a frame or use it sitting down (perhaps you could get a used one, or wait for a special promotion where they have special financing or a free frame). You would probably be able to fit the machine in your RV and the extra throat space and regulator would allow you to do quilting while traveling but would have to be off the frame. I have the Grace frame, but I do agree with the others, that even set up at the small size which is about 5 feet, it wouldn't be very portable.
I did have a Juki 98 on a frame and it was a great machine, but only 8 inches in the throat. The Bernina has about 13" and it really makes a big difference.
So, I guess you really have to refine what you are looking for, and will the RVing be a deciding factor.
Good luck, and don't forget to let us know what you decide.