Really, it's a matter of personal preference. Some people prefer quilting on frames; others prefer a sit-down machine.
I have a midarm on a frame and find it's a lot more fun for me to quilt that way. I don't have to have a large flat surface to baste the sandwich, and it's easier for me to move the machine than to move the quilt. I also like being able to stand up as I quilt -- much less fatiguing for my back, neck and shoulders.
There are people who prefer to FMQ on a sit-down machine. One QB member actually changed her frame setup to sitdown because it was easier on her body to quilt that way. I have met marvellous quilters who have never quilted on a frame setup; they learned to quilt sitting down and they just wanted to continue that way.
If at all possible, go to a large quilt show and try out all the different setups there. Find out if you like quilting by moving the machine. I loved it the first time I tried it, so I knew I wanted to go with a frame setup rather than a sitdown. If for reasons of space I had to give up my frame setup and go with a sitdown, I would definitely use a suspender system such as the Jennoop to make it easier. If I had my "druthers" for my dream quilting setup, it would be an Innova with lightning stitch.
The BlockRockit gets good reviews from users. You might want to join the homequiltingsystems group at groups.yahoo.com; I have seen comments about the BlockRockit there.