Most major brands are reliable. I would also look at where you are going to take it for repairs/service etc....Some tractor mechanics are very opinionated about ease of repairs on certain tractors.
Congrats tractors are fun. I wouldn't ever let a dealer or service be a deciding factor. I've had many tractors and actually have four right now. I've never had to take one in for repair and have had very few minor repairs that I fixed myself. Of course there's probably plenty people that either don't want to repair maintain they're own or have the ability. This would be a concern if someone was in that group I reckon.