I've had my 36 over a year and love it. I read a lot of people say they wish they would have gone with a larger unit. I guess I am one of the few that is glad I have my 36 and doesn't want a larger unit. I like to smoke 2 to 3 weekends out of a 4 week month. I usually cook for just my family, but occasionally cook for relatives and friends. I cooked a brisket, a few butts, three racks of ribs and some fatties all at the same time for Christmas last year for my entire extended family. Now, the 36's come with slide out top rack, a very nice feature mine doesn't have. I guess if you are going to cook more for larger crowds on a consistant basis, it would make sense to go with the 48. If what I do sounds like what you will use it for, then you won't regret the 36.
I do plan on selling my 36 though.......just to get a 36 hybrid deluxe. I usally use a Weber Gold kettle 22.5 for my burgers, steaks and hot dogs, even though I can get grill temps with my 36.I would just like to have one unit that I can do everything on, whether independantly or simulataniously, plus I like the idea of having the warmer if needed.
Hope this helps.
Rusty