The SF model is the short frame. The distance from the backstrap to the trigger is about 1/8 inch shorter. Other than that I don't believe there's a difference (but I'm not a Glock guru).
3mm difference front strap to back strap. Some folks can feel the differeence some can't. I have a G30 and a G29SF. (same frame) I can notice the difference. The SF just feels a bit better to me. I have average hands.