What's your budget?
I agree with Hex. I'm in the same boat as the OP and currently have a Char-Griller horizontal offset that is modified.If you're only wanting to do a couple rack of ribs or one butt, a Weber would be my best advice. In my experience, the Char-Griller type smoker/grills aren't very efficient, and don't do either very well without modifications.
What size would you recommend? Also, what temp can you get it down to?Weber all the way