Here is my 2 cents on the Ex 21. I am new as a lawn care business but have cut grass for money or just to be nice since mid 80s or something. I had a big box store gift card this summer so I went that route and had problems with 2 different pushers. I decided I wanted a commercial warranty of one year minimum. Spent around one day hitting the net, calling, etc. Came close to getting a Snapper, but found later that it was not a year commercial warranty. Found at that many dealers will tell you info on warranty and be totally wrong. Even reps from companies told me wrong. I looked up the warranty on each brand via their company web page and ended up with Ariens or Exmark as my last 2. Found an Exmark dealer close to my house and decided to go that route as many people had told me Ex was the best. The final straw was calling a guy near my city (who didn't know me from Adam) who said the Ex pushers were unbeatable. He preferred another brand for Z-turns, btw, and said the Ex 21s hold up well because his crews beat them up pretty good.
I bought the last 2010 Ex 21 pusher they had on the floor to save money. This is the heaviest pusher I have ever used (about 120 lbs), but also the most powerful. The self-propulsion will literally pull you up a hill and gets hardcore grip with the rubber wheels. Both engagement handles are harder to hold down than average, but the machine doesn't stutter at all. I ran over a small stick today and got ready to hear the CHUNK but it sliced that thing clean with no sound. It is basically like a small tank with a high RPM samurai sword. It has a primer so it's not the quick crank type deal. The height adjustment is not a quickie, either, so you can't do the adjustment on the fly like some others. It is some work to deal with the weight, kind of like driving a boat, but I just cut my back yard for a wedding and it has never looked this good. So the 2010 Ex is extra work, extra money, but the grass will look awesome. Also, if you are going to mulch with an Ex bagger, get a mulch plug and the mulch blade. The blade that comes with it is for bagging and you need the plug to make it mulch right.
The 2012 is lighter by about 15-20 lbs, other than that, not sure of the major differences. Hope this helps. :thumbsup: