Most quilters have a definite preference for one or the other. How long have you been researching your purchase? The rule of thumb is to spend a year looking and trying out different setups before making a decision.
I learned to FMQ on a domestic machine but always felt quite tense doing it. Once I tried out a frame setup at a quilt show, I knew that was what I really wanted. For me, quilting on a LA is easier on my back and shoulders than quilting on a domestic, probably because I am much more relaxed. I have never been able to machine quilt for hours at a time - an hour or two per day is my max. This may be part of the reason my back problems have not flared up from quilting.