Still looking for the right used Grand L and wondering if I should expand the list from the larger L6060,5460, and 4760 to include the 4060. I felt I wanted the larger models to use the LA1055 loader with higher lift capacity than the 4060 with the LA805. But if I only load the rear tires of these models for ballast will the higher capacity of the 1055 be safely realized?
Short answer - fill the tires.
My previous tractor was an L3200 with the LA524. It was adequate for most of what I wanted it to do, but sometimes it would have been nice to have a few hundred more pounds of lift. It had loaded rears and almost always had something om the TPH.
My L4240 has the LA854 loader as does my BIL's L4740. The capacity of these loaders fall between the two you are considering. Both of us have liquid ballast in the rear tires and usually have something on the TPH. Both of us generally have mowers on the rear all Summer. Winter TPH implements range from nothing to blades to (in his case) a blower.
I've used his 4740 and it feels just a tad more powerful and larger. I remember stepping down off of his tractor and getting tripped up a bit. I didn't measure to see if his step is higher so don't know if it was my lack of agility or muscle memory of mine being closer to the earth.