J - Dave is absolutely right. I've done as large as an 11 lb pork butt, or 3 racks of back ribs, or 1 large chicken, or up to a 14 lb turkey. You don't want to overload the #1, as you will sacrifice cooking efficiency and smoke penetration (both need space).
I think the real question you are asking is what model to get...right? Here's my answer: Let your needs and budget determine which to get. I initially bought the #1 based solely on budget. SI, and electric smoking, was a total "unknown" for me. I didn't want to sink a lot of money in something I wasn't sure about. At the time, this forum was very small, and pretty new. There just wasn't the wealth of information there is today!
Had I know what I know now, I would have ordered the #2. I absolutely love my #2.
Needs: How many folks do you normally cook for? I only smoke for 3, so the #1 actually fit that bill just fine. What the #2 gives me is "overhead." Having more space allows me some flexibility to smoke more than needed, if I choose. While I would love to have a #3 or 4, it just doesn't fit my needs. I could probably justify a #3, but not a 4. It would be nice to smoke whole, large, packer briskets.
Budget: Let that be part of your decision (duh). If you can swing a bigger model, get it...you won't regret it. You can always smoke less in a larger one, but can never put 4 gallons in a 2 gallon bucket!
Hope this helps!
