WSM's are great!!! Very easy to use and almost no interaction! If you are going to buy a smoker that is the way to go. I have seen people win comps with them over big old Langs and the likes. Can't get a whole hog in them but great for the back yard BBQ. They have the bigger one now also, almost as big as a drum!
If you are a little handy though I would recommend building a UDS, costs alot less money and you have a 55 gallon smoker that pretty much works just like the WSM and you will have $150.00 or more left over to go buy meat
I like the MES also but you have the whole electricty thing to think about. Not that that is a bad thing but they have been known to break on occasion. Both would be a good choice but I would have to go with the WSM just because it will last forever without question..