review your options; how long are you outside on the gator? How much money are you willing to spend? Is it cheaper to buy a good coat, some thermals a hat and some gloves or would the doors be better? I personally prefer the sun and wind hitting me while I'm out but I'm in Az and when I'm working on the gator it's for pleasure not work/job. I did have an angry Tom turkey give me the business when I came too close to his hens but if he was truely pissed off, I doubt the door would have stopped him
If you are referring to the Glass cab and doors, it's amazing. Very airtight and holds heat VERY well! If you are refering to the poly cab, it's a nice cab but not very airtight as it's a poly plastic. With the heater, it makes for a nice cab but the Glass cab is SOOOO much better.
But just like gatorvirgin said, it's how much you want to spend!