You might be able to get by with a 3pt scoop. Lots of people use those and are happy with them. Not the same as a FEL, but can still move a lot of material. If you do decide to get a FEL, I would let your other uses determine which tractor you put it on. If you need your bigger tractor for lots of pulling or mowing, put it on the smaller tractor. Or vice-versa. The compromise with a FEL on a tractor (especially 2wd) is maneuverability. So if you need to get your smaller tractor into tighter places, put it on your bigger tractor. Transmission might be a determining factor, too. If either of your tractors has a hydrostatic transmission, you would probably prefer that one to have the loader. If they both have the same tranny, then no difference.
You have two good tractors, so you're already pretty lucky!