i like heavy irons with NO auto-shutoff. The one I currently have is medium weight and have the most annoying auto shutoff. after 4 seconds horizontal with no movement, it shuts off. I can't keep the iron on my applique pieces long enough to fuse them before the durn thing shuts off. After 8 seconds sitting still on the board, it shuts off, which means that I can't really move to go get my next piece of fabric and back again to iron it without it shutting off.
so, I would advise you get one that does NOT shut off on you!