For an average rider, the difference between having the snaps and not having the snaps is negligible. Most folks wouldn't notice the difference.
Just for the sake of sharing information though. Yes, the snaps make subtle communication more difficult because the horse learns to ignore the more minor shifting of the weight in the reins. With snaps, the reins are always moving and clicking and swinging; MUCH more freely than they do with just the water ties connecting them. The horse learns to tune out that smaller vibration and movement and that means you have to be more obvious and bigger with your cues.
Hmm... I bet that is so right. Originally with these reins I did have water ties. Loved them... except when I was walking Snoty by holding her single rein, and it just popped and broke! Whoopsy. The guy that made them said that he had never done them with a water tie, only with a full braid going over the scissor snap, so the hole must have made a weak point in the leather which broke. He replaced them for free, so that was nice. :) I can't remember a change in her listening being noticeable... but like you said, those of us who are novices probably wouldn't realize it! But to that idea- when I have flat leather reins, she takes all sorts of advantage of me! LOL I used to get yelled at during lessons for absentmindedly fiddling with the leather, or losing the right spot on the rein... then off we went to somewhere my horse wanted, but I didn't... usually right to the arena gate, as she hates arena work. lol