I have a 57 PTO tractor. I thought I wanted a 4x5 (4' wide x 5' diameter) but couldn't find one. I did find a 5x4 (5' wide x 4' diameter) that I purchased in great shape considering the age and price was right......basically a downsized (reduced diameter) bale that one could roll with a 5XX series JD baler choked down from 6' to 4'.
I have some 4x6 bales that I bought (before I decided to bale my own again) and some 5x4's that I baled. My best guess is that my bales weigh in at about 800 and the 4x6's more like 1200. The grasses are different; mine is Bahia and Pearl Millet and the purchased is rye.
The purchased hay lasts about twice as long in the hay hoop as the grown, but I think it is due to the fact that they won't get off it like they will the purchased. The purchased is net wrapped and mine twine so it seems to weather better for long term storage. Even though the net is a superior wrap for down here, I am familiar with the twine and the price is right. For the big boys, go for it!
My hay patch is pretty level so I don't have terrain to contend with. My baler is the JD 375 and is totally manual; everything is visible on the front of the baler and you manually activate the tie function and make the tie.
My last, previous baler was a JD 530 making the 5x6 rolls and was automatic with a monitor in the cab and an automatic tieing system. Being 30 or so years old, age took it's toll and the tieing function was unreliable even though I went to a lot of trouble to fix/get it fixed.
Personally, I like having control of everything myself. Nothing to get out of adjustment or break which saves me money, frustration, and time. Being retired and a small operator, I don't need to be fixing things and spending money if I don't have to.
One benefit of the smaller diameter roll is that it is easily carried on the FEL on the smaller tractor (than I had with the 530 baler) and seeing around it isn't the problem it was when I baled 5x6's.
Other thing I think is the size baler I bought has a niche buyer's market and not many folks are looking for them. I bought mine from Southwest Auction Co., Inc. in Howe, TX. and there were 2 on the lot. There were several newer JD 5XX balers but no 4XX which bale the 4x roll I originally wanted. I did enjoy a round of haggling on the price which I enjoy when making a major purchase of farm equipment.
So, that's my story.
Hope it helps,