The way my dealer explained tractor model to me is like this. Tractors don't change year to year so it's the "year" a tractor is sold that most people will reference. A new tractor could sit on a lot for awhile before being sold as new. That skews things a bit. I was told to look at the serial number. I don't know what the differences are beyond the number of lug nuts on the front wheels, but if you PM me with your email I can send you parts guides for both and you can compare.
I forgot to ask earlier, is the tractor 4 wheel drive? I assumed it was when I commented on the price.