I usually use a 14-16" round hoop in my lap. I hand quilt anything from baby to king size quilts. I've also gone hoopless on occasion but having it in the hoop makes it easier for me to find where I left off my last quilting session. I've not noticed a difference in consistency in my stitches either hooped or not as I generally have my sandwich quite lose in the hoop.
I, too, hand quilt year round in this fashion and it gets mighty warm & humid in these parts come summer!