I don't know anything about the Viking, but I am not giving up my Juki for anything! I want to get a long arm, but when I do, the Juki stays for piecing. I LOVE everything about this machine.
I use it on a frame, but I can't imagine using a Qbot with it. With only a 9" throat, by the end of the quilt you end up with between 4-5 inches to quilt in. Not alot.
That said, if I could find a long long arm Juki, I would buy it. As long as you remember the magic words "Juki Loves Oil" everything is great.