Here's another thought. It is not clear, at least to me, what you actually want to do with this tractor, or put another way what do you expect the tractor to do? Try making a list of "must do" then "nice to do" maybe even "not needed now / and or ever" For example, within reason the 3x20 will do many of the same things as a 4x20, maybe some even better, but there are others it will not do. On either series you can have the FEL with Buckets / Pallet Forks / Grapples / Snow Blowers / Blades etc. One question with all these implements is "how fast" or "how much weight?" If lifting Round Bales will ever be a "must do" the 3x20 won't.
Same with PTO type equipment. Either series will run one. Is smaller / slower satisfactory or do you have to have bigger / faster? Same with ground engaging jobs and / a Back Hoe. Another factor is the larger the tractor, chances are the bigger / faster implements will cost more as well.
In my case, I wanted certain minimum lift capabilities with the FEL and digging depth with the Back Hoe. These requirements ruled out the 2305 & 2x20 series, but for that I had to compromise on the lawn mower aspect of the 3x20. If you come up with one or more "must have" capabilities and that also fits within the budget, then you will have picked the series and model best for you.