I debated the same thing btwn a WSM vs a Vision. I chose the vision because of the versatility. I use it to smoke, grill or bake...which 90% of the time is fine. But when I threw a birthday party and had to do 2 things at once, I had to break out my old Kettle. I was using the kamado to slow cook chicken, and the kettle to grill corn and pork.
So if you already have a kettle grill, it might be better to go with a WSM. If you dont, then start with the Akorn.