The manufacture of the machine is no more important on the longarm side as it is on the piecing side. Its all about the experience/skill level of the operator. Demonsrating the quality of the finished work is important when I make my choice for who does my work. I measure quality by the consistant stitch lenght, the overall evenness and fill of the quilting pattern, the appearence of the backside ( knots etc), comitment to a delivery schedule, willness to work me to determine the best stitch design to compliment the piecing these are just a few things I use to determine my LongArm Pro. I have known many a piecer with high end machines who's work was ... well ... leaving room for much improvement.
Cost is a factor , but not on the top of the list. I look at is the cost resonable for what is expected.