I have no experience with the WSM but love my Akorn.. The versatility as mentioned is great but the majority of my cooks on it are Low and Slow. I would have been extremely happy if the Akorn was only capable of smoking based on its efficiency, ability to peg a temp and stay there as well as the moist cooking environment.
One thing with the Akorn is not all units are perfectly adapted to low and slow from the get go.. Most require a roll of Nomex gasket to get it really sealed up tight. Additionally you must purchase some sort of deflector in which their are many tried and true methods from the weber grate and a pizza pan or stone to the Akorn Smoking stone.. One piece of equipment for the Akorn that I do not think I could do without while smoking is some form of digital thermometer. The supplied thermo is junk for the most part and the whole key to having consistent temp in the Kamado is keeping the lid closed, the remote thermo aids in this. .
I have had my Akorn around a year and I could not be more pleased once I got through the learning curve and have her all sealed up.. I can run the entire BBQ temp range from 300 all the way down to 225 with very minimal babysitting. The Akorn uses barely any lump and is extremely efficient when running low temps.
As to the portability, its not bad. The girlfriend and I easily lift it in the back of the truck. The only problem I see with portability is having adequate time to snuff the fire.. It may lead to disaster if the charcoal was not completely snubbed and you got her going 55mph and had a small air leak.
You are comparing to cookers both capable of turning out great product. You need to look at your stable and identify what you want from a cooker and than make your decision..