A good place to start would be to read all the posts in the Who, Where, What did you start with forum. Take a look at what we are all using and take an average of this. What is best for one company isn't always the best for another. The reason I use the equipment I use is I feel it is the best or I wouldn't have bought it, but that doesn't mean the next guy thinks it is.
If you have a dealer around you like I do, that also has a mowing business, this would be a good place to buy. You know this dealer will stock parts for his equipment, which means he will also have enough in stock for you too. He has already field tested what he sells, in my opinion this is the best place to shop for equipment. Dealer service and parts availability is very important to keep you from having down time.
He sells:
Dixie Choppers
Exmarks
Shindaiwa
Red Max
Except for Exmark, this is what I use.