I have a
L3200, same frame & loader as the
L3901, just less HP & emissions.
I can fill a 250 gallon IBC tote over 1/3 less than half full of water before the loader stops lifting it. 1/2 full = 1,000lbs. Add a couple hundred lbs for forks & 50-100 for the tote plus the fact that IBC tote sticks out 3' & the rated capacity is about right.
I've helped a neighbor move some big rectangular bales. No clue how heavy, but they felt about as heavy as my IBC tote I think. Those bales maxed out my tractor & moving them was a little sketchy. I kept them low & went really slow. I'll help him in the future with his remaining bales, but neither of us wants to deal with large bales again. He got rid of the goats & is selling the remaining hay, but would have gone to small bales.
At any rate, while a L3xx0 or L3xx1 tractor will barely do it, it is not an appropriate tractor if you are planning on moving big bales. It's just not that safe or enough tractor. A 4000 series would be the minimum I'd recommend, probably even a 5000 series.
As others noted the L 00 & 01s are economy models. The Grands (40 & 60) tractors have more weight & capacity than equivalent economy models, not to mention other bells & whistles.
Weight defines how much a tractor can do. HP just defines how fast it can do it. Compare weight of a machine before you compare HP