Re: Difference in the Stem
you might notice a slight difference in hit. i personally don't unless i'm trying to detect it. a bit like, noticing the difference in the air you breathe where you live, and the air you breathe when you go to the wilderness.. (creative imagination there)
you'll love the small one for ease of cleaning (which you'll do a lot of and appreciate). i've had a range of hookahs (8"-36") and have downsized to a single, Mya Bambino. no regrets.
i believe, the small gelato is all you'll need.. especially since it's multi-hose convertible.
good luck w/ the decision. you can't really go wrong.