I would recomend the following: buy what you like, and what you would like to keep. If you make a lot of repairs or updates, you may not get that money back other than through enjoyment during and afterwards.
We have about 20 tractors on the farm that get used, and a couple to play.
2 cylinders are fun, and the older ones are affordable to fix. Not so much the diesels, at least the fixing part. (Playing with them is always fun, repairs, expensive.)
My two toys- a 36 A that I bought 17 years ago and restored. It turns heads where ever it goes, and the battery is never dead. And useful for nothing.
The other toy is a 64 4020 powershift with M and W turbo. It is good original, and oh it's fun on the no-till drill. And it needs a few minor things, and they may cost what I have in the A.
Decide what kind of fun you want and waht the budget allows. One of the most fun farm tractors we have is a 50 A that my grandfather bought new. Char-lynn powersteering and work clothes make her useful. Not like the 4450, but useful in it's own way.
Good luck in your decision.