BadBoy mowers are very maintenance friendly and good quality, they can be found at about 1/4th of the Tractor Supply stores I've been to as well as online. Dixon is the company that actually coined the term "zero turn mower" and has been in the business nearly longer than anyone, they have dealers various places. Cub Cadet has been in the "zero turn" market longer than just about anyone (before they were called zero turn mowers) and they can be found all sorts of places. All three are worth a look before committing to anything.
While I can't give model specific opinions on your choices, my overall thoughts on the brands mentioned above:
Anything as small as a zero turn by Kubota or John Deere isn't manufactured by them. The high end models they have the parts made by third parties (lowest bidder) and run it down their own assembly lines to have the benefit of hands-on Quality Assurance. Their lower end models are all manufactured and assembled by the lowest bidder, painted to look like a John Deere or Kubota and have a huge price markup placed on it to cover warranty services after the sale. I'd find the equivalent model by a "lesser" name and save a buck or two unless there were some key quality differences on certain components. I have 42" Craftsman and John Deere tractors that are the same age, same frame, same motor, same deck. The only differences on the machines are the design of the spindle where it attaches to the blade (simply to make blades non-interchangeable), the locations of the gas tank and battery are swapped, the JD has a garden hose connector for a deck cleanout, the Craftsman has a hydrostat and the JD a gear drive. The JD gear drive was $200 more than I got the Craftsman hydrostat for, and an identical JD hydrostat would have been $400 more. Needless to say I kick myself for buying the JD considering it travels the same ground as the Craftsman and is broken down twice as often. If you need a $50k+ piece of hardware, JD and Kubota are worth a look; but on the small stuff they don't manufacture, the better long term investments are found elsewhere in my opinion. While it's just 'luck of the draw' that my particular JD breaks down more than my Craftsman; my point is buying it just cause it says JD on it (or Kubota for that matter) doesn't mean it will provide trouble free service, it just means it costs more overall. The main reason I can see to go with JD or Kubota would be if you have really excellent dealers in your area. An excellent JD or Kubota dealer that makes the purchase worth the price after the sale is the only REAL reason to pay their prices for their hardware. The quality of service from a high quality JD or Kubota dealer really can't be matched by dealers of any of the other manufacturers. On that note, if you have a high quality locally owned mower repair shop in your area, they can fix any of the zero turn units as well as any dealer can and do so at way less cost simply due to less overhead costs (owning a franchise dealership costs gobs).
Swisher is a good company that manufactures most of their steel work and purchases high quality components and hardware for final assembly. What they purchase from third parties is likely from the lowest bidder same as John Deere and Kubota, but the standards of quality seem to be higher (likely due to their focus being on their large equipment). John Deere and Kubotas generally have "prettier" appearance than Swisher on the machines I've seen, but the Swishers seem to be more stout of a machine (heavier gauge steels, better powdercoated finishes, thicker welds).
eXMark is now owned by Toro. Before settling on this model I'd check out the equivalent Toro and see which has the higher quality components. Beyond that I don't have any experience with them (or Toro) to advise or comment any further.
Hustler is another oldie that was early in the production of zero turn mowers and they've been in the mower game as long as Cubby or Dixon. They've always catered more to the commercial segment and I've not had any experiences with them but I'd say they're surely worth a look.
Myself, I'd go to a company whose lifeblood is mowers of the size and type you need who also manufactures their own designs. I think all these brands mentioned are selling good quality hardware overall, it's mostly what is going to be the best overall value for you and your needs. One of the best pieces of advise I can think of, test drive them all. As with most equipment you never know what you'll think of it until you have it in operation. SEAT TIME!
