The biggest criteria, for me, would be who has the closest dealership for parts and service.
Very good point. And it's not just how close they are, but also how good they are to deal with. A good parts man at a tractor dealership who can identify and order what you need can save you a huge amount of equipment down time, especially if you have the parts book for the machinery and can ID and order over the phone.
The closest Massey dealer is only 5 miles from me, but they are such a pain to deal with we go 20-25 miles to a different one instead. And we're lucky that the JD dealer and the Ford/New Holland dealer, while 25 miles away, are only 1/2 miles apart.
The JD tractor dealer will have parts shipped direct to me if they need to order them from the next level of distribution. This is a good time saver. IIRC any JD dealer will do it; perhaps other brands as well - it's worth asking about.