Just wanted to put my 2 cents in on what a b series tractor can pick up... here in Nw Pennsylvania a 4' x 5' round bale runs between 800 and 1000 lbs depending on how much moisture is in the hay. I have successfully strapped one of these beasts to the bucket of an LA272 loader on a
B7500 and toted it around the yard with great success. I doubt if it was beneficial to the tractor in any way, but it didn't seem to hurt anything. If I could figure out this computer stuff I could post a photo of it... anyways, that little
B7500 was one heck of a work horse. I now own a
B2710, and let me just say that the difference in power is astounding. The 2710 seems like twice the tractor the 7500 was... (not trying to belittle the 7500 in the least, mind you).
With that said... and now knowing you use much smaller bales, I would definitely say that anything
B7500 and bigger in the B series would suit you fine... It seems like most of these tractors are all capable of completing similar tasks, it just takes a little longer sometimes with the smaller models. IMO, you should buy the biggest B series that your wallet will allow.