Just about everything has a downside.
A lot of seasoned pit masters point out the importance of a sufficient amount of meat in the pit for the sake of moisture. Just think about this, in case you ever plan on cooking with a dry pan.
As far as capacity and cooking for crowds goes, the little wsm that Weber has been making since 1981 has been enough for a BIG party! For instance, start off with four butts at a total of 32 lbs to give you almost 20 pounds of pulled pork. Of course, I've read on a serious bbq competitor/caterer's website that he has added a third rack and squeezed NINE butts on one of his little wsms before! That's a lot of BBQ! Restaurants plan on 5 sandwiches to just one pound of pulled pork.
On the other hand, if you want to start catering or cook whole pork shoulders, not just butts, go with the 22 incher, and cook a LONG time. You can cook BIG beef cuts in one piece as well, but....why? It's been suggested that you can cook the biggest brisket you want to on the little wsm by cutting off enough of the point to make it fit and laying that chunk of the point by the rest of the brisket, getting done at the same time as the flat. (As far as ribs go, I can cook four racks of spares layed flat, or six with racks with my little wsm.)
Anyway, just food for thought...either way you go, you can't go wrong!