I'm a charcoal purist, so I can't help on gas grills. Personally, I use vertical grill/smokers due to space limitations.
I've owned several Brinkmann Gourmet charcoal smokers and a Weber Smokey Mountain cooker.
The Brinkmann is more versatile, but the Weber is the superior smoker.
The first link is to a good site for info. It's directed to mods to consider for the Brinkmann, but the whole site is great.
The below link is peculiar to the Smokey Mountain, with discussion forums.