I dont do long arm.. probably never will because its not something i could really ever afford (i would love to try it one day though). Im assuming the reason why there isnt "puffies" on a long armed quilt is because its on a big machine that holds the sandwich taut(sp) *im only going by pictures* :P I do lots of basting especially since my quilting is done by hand or on my little home sewing machine. Mine get a puffed look too and to be honest every person i have made a quilt for actually complimented the puffy look. says it makes it look huggable :D.
Honestly i think either way makes a quilt look beautiful but im biased.. i love quilting XD.
You should give it a shot! I have been planning to quilt from the back on one of the upcoming quilts. It seems like it will be fun! I cant wait to see your work if you decide to do it!
Good luck!