With no use requirements other than HP...only summary info is provided:
60 hp at the PTO is a transition area for Kubota.
Kubota L series:
Max out at about 60hp...smaller frame, smaller utility tractor, loader work, mowing, limited agricultural, not targeted for heavy ground engagement tasks.
Kubota M60, M5, M6 series:
50hp and up, typically larger frame, heavier, targeted as agricultural use tractor
Kubota MX series
50 to 60 hp, targeted as utility tractor and bridge between L and M series.
If you're serious, search YouTube for "Messicks" for some short, informative videos on the Kubota tractor product line.
Good Luck!