Hi Ginger,
Since I have a model 1 and a model 2, I'm probably qualified to address your questions!
Short answer: Get the #2 if your budget affords it. And, in my opinion, yes to the cart (makes life a lot easier).
Longer answer (get comfortable):
I bought the #1 due strictly to budget reasons. I had never had a "real" smoker (always made-due with makeshift smokers in the past), but didn't have any idea how this would work. So, I wanted to go the cheapest route and bought a #1. While I was very impressed with the smoker's performance, I have never been impressed with the size. If you look back at my earliest posts on here, you'll see that from the beginning. I smoke for me, my wife and son, on a regular basis. Occasionally, I cook for more.
With the #1, you can do one whole pork butt (8-10 lbs) at a time. You can also do a full packer-cut brisket, if you cut it in half. One large chicken, or 3-4 racks of baby back ribs. For a turkey, you can fit a 12-13 lb bird in there.
Enter the #2: Wow! What a difference a few inches makes! The shelves are 15" x 15", and there are more of them. Room to breathe! I like the larger element (700 w vs. 400), and the vertical height inside, also. Even smoking for 3 people is so much more pleasurable with the #2! I'll still smoke the same amounts, but don't feel like I'm having to shoehorn the meat in there! I can now do 2 butts at a time, and more of everything else.
I believe you would be happier with the #2, but the #1 is a great Q producer, too! Both perform flawlessly, but I prefer the size of the #2. I do not need the size of a #3, but wouldn't mind having one - just to fit full briskets in, without cutting!
Let us know how else we can help!