I've done both - moved the fabric while the machine stayed stationary (on the Flynn setup) and moved the machine while the fabric stayed stationary (Inspira setup) and I prefer moving the machine. Even though the work area is smaller, I don't have a deal with managing the quilt.
I sold my Inspira some time ago, it just took up too much space. So now I'm looking at getting either a Juki 980Q, or a Jamome 1600P, or an Elna 7100 - all have 9" throats, and the EZ Track Quilting System (
http://www.easyquilter.com/index.htm). The set up wouldn't have all the bells and whistles of the more expensive setup, but it is sit down, and I'm fairly good at FMQ, and the investment is less than $1500 for the machine and the EZ Track. I could handle that.