We got the 22" because it has dual burners, so you can cook at different temps (or just leave things warming if you turn one side off).
Not much bigger or heavier than the 17".
A lid is really nice...if nothing else to keep debris off when not in use. Ours didn't come with one, so I picked up a big aluminum sheet pan and it works well flipped upside down. I'm still experimenting but I've been able to make pizzas with the lid on.
For home or permanent site, the big 36" or bigger models can feed a small army but way too much hassle for a mobile situation.