My dad owns a Lawn and garden dealership that sold Dixon and Ariens. Here's the long and short of it Dixon and Dixie Chopper used to be combined but seperated and did there own things, both doing ZTRs. It is our opinion Dixon is a better machine. Ariens is a very good amchine as well, equal, I'd say. There are companies that advertise they sell ZTRs but they are not TRUE ZTRs, wathc out for those. Another thing for manuverability and better cut get a model that has the deck under the body of the machine, not in front, this is not an issue on dixons or Ariens as every one we have seen is that type.
The low to mid range, most use mechanical cones to drive each wheel, these last quite awhile, especially if you dont tow anything but steering is more "jumpy". Upper end units use hydrolic pumps to steer and are VERY precise in steering. We used a 60" 20HP commercial dixon as our "demo" ($7500 5 years ago) You could mow around a dandilion and not hit it. They are WAY FUN to use, at least the big hydrolic ones are and are built like tanks.
You can get lots of accessories for them to.
Most engines on those machines have pressureized oil now, even alot of low end ones. Try to find one that has a Kohler engine, they are closly related to Onan engines and are better than Tecumseh or Briggs but NOT as good as Honda. Briggs are the bottom of the barrel these days.
Now, if you have flat lawn with few trees, flower beds etc. Ask your self if you REALLY need such a machine, most dont BUT if you buy quality now, you wont have to later, and hell, they are alot of fun!
Hope this helps!,
BrenLover