I have the 18.5" WSM and bought a BBQ Guru DigiQ II model when they first came out. I did not see the need for wireless back then, but might consider it now. I have the 10CFM fan on mine which is plenty for the 18" WSM. Once you use one, you will never consider going back. It is about as close to fire and forget as you can get with a charcoal or wood smoker. Mine holds 225* as long as their is fuel left and I have run 12 hours on a full WSM fire ring.
From what I have read, the 22" uses fuel a little more rapidly than the 18" due to the volume to be kept at temp, but on a 16 to 18 hour pork shoulder smoke with 4 large shoulders (8 to 10 pound each), I only have to add coals & water about 2/3 of the way through and that is mostly for peace of mind while I sleep (I usually start shoulders around 2-3PM with intent on pulling and resting in a cooler by 9AM, ready to pull by 11AM or so). No fiddling with dampers or checking it every hour or so. Once you learn your pit's pattern on a Guru, it's pretty much auto-pilot and repeatable every time.
IMO, they are worth every penny. Again I have a Guru, but any brand power draft would be a plus on a pit.
I would recommend you go with a model that lets you monitor both the pit and food temp, otherwise you will have to use a Maverick or other unit for your food. Keep it simple with both in a single unit if you can.
The DigiQ DX2 is the current equivalent of what I have. Looks like they are $271 now, with 10CFM fan, WSM adapter and the standard 6' probes. This unit lets you monitor both the pit and food temp (single pit and single food probe).