My Deere salesman says he finds the quality near equal to the Deere of the same size, and thinks that because less $$'s, get a better deal. He has sold a bundle of them to mostly commercial buyers. Also, I think he said there was a smaller size than the Deere models that sells well.
There are a lot of other "popular" brands that he takes in on trade, only if he has to, and they don't compare to either the Deere or the ExMark. But you can make your own decision what is best for you.