Lots of opinions here, and not all facts are correct.
Cub Cadets have Kohler engines. Ask your dealer how many have burned the house down. Mine almost did. First time in my life I ever had to run for a fire extinguisher. (they say its corrected now, but are ya feelin lucky?)
Deeres have their own engine brand, but they are made my Briggs. IMHO since B&S has stood the test of time, that'll be what I personally buy.
Depends on what size tractor you want to buy. If its a relatively small one, the model that Home Depot (or other box stores) sell is exactly the same as the one the JD sells. If you want a bigger one, you are stuck with the JD dealer.
Buy a JD online and you might get free delivery.
Zero turns are nice, but the current "regular" tractors have an amazing turning radius, so I would not buy one at that elevated price.