My experience with tractors goes something like this. It's much cheaper to buy a tractor that's configured the way you want/need it to be than it is to buy one that isn't and start modifying things. Of course there are various attachments that you may add over time, but make sure it already has a loader, AG tires (make sure the tires have never had calcium chloride in them), hydraulic circuits you want, and the load carrying capacity to perform as intended. I wouldn't go out and spend $16K on a tractor just to use for firewood and then justify it with the buy once, cry once logo, but I would make sure that I bought something big enough to do what I wanted to do with it AND new enough that it was still somewhat serviceable.
What equipment would work well for you really depends on exactly what your circumstances are. I mainly cut hickory, oak, and locust, and the trees range from 18" to just under 30" at the base. I trailer my firewood (in log form) quite a ways down the high way (over an hour with a load on), so what works well and what doesn't work worth a darn is going to be different for me than for someone that mainly cuts 8" to 16" Ash on their own back 40.