Re: the bigger the better?
Taller stems do offer advantages, but it isn't always the best choice. My QT can produce very good smoke - on par with my 27" Syrains.
Typically the taller the stem, the longer the smoke has to travel, allowing for it to kool, which in turn provides more flavor and easier to smoke.
If you plan on traveling or must pack away your hookah (rather than have it sit out for everyone to see) smaller hookahs are the way to go. Most smaller MYA's have cages/cases for storage and break down into many smaller pieces. Even other versions of small hookahs (22" Egyptians or Syrains) although can not be broken down as much, are easier to carry and store away.
Another thing for consideration is price. Larger rigs typically have larger price tags, which also means (but not in every/all cases) they can cost more to order & have them shipped.
So yes, a taller hookah does look nice, can help with smokability, smaller hookahs have their plus points as well.