My advice is don't go to a box store like Home Depot, Lowes, Walmart, etc. They sell junk that is cheapened up to appeal to consumers that only shop for price and don't care that it won't last very long. Yes, John Deere makes great tractors and mowers, but they also build cheap junk and sacrificed their reputation to chase after the general consumer that buys only based on price and name recognition.
Tell us a little about your situation. How much area do you mow? Is it lawn or pasture? Why type of grass/vegetation? Hilly or flat? What's your budget? Do you want a lawn tractor or a zero turn?