Are you planning to use the machine ONLY on the frame?
If so, I would probably opt for the Juki. I have the Pfaff 1200 Grandquilter which is very much like the Juki. It is a straight stitch machine which only goes forward and backward - but it does so very fast. It has a nice throat size and is made for quilting. There is a cruise control available that is like the stitch regulator.
The Babylock (I have an Espire) is more of a regular sewing machine with lots of features including quilting features and I would be tempted to use it for all my other sewing needs as well.
Once you put the machine on the frame, you'll probably leave it on the machine (except for maintenance).
That's my 2 cents worth. Either way - I don't think you'll go wrong.