While i never owned a ck2510. I was choosing between the ck2510 and the 2610. I went with the 2610 because i thought the heavier weight and bigger frame would be better for long term use and maybe handle a bit more work. That said, The HST on the 2610 i find in no way what so ever jerky. It is smooth as a puppies belly. I know its not safe, but there has been times where i find myself on the ground and need to move the tractor an inch forward or back. With a bit of pressure from one finger i can make small adjustments as needed and it moves slow and steady. I think the 3 speed hst is the big bonus here. Often, i run in the M setting or the L for when i am plowing or scooping dirt and working it. But if i am just driving around property with a load of horse manure i keep her in M and she runs great. H is really only good for the road or down a good lane. Not much power just good speed. I always run my kioti at the 540e notch on rpm gauge unless i need power for rotary implement or cruising down road.
Of course it could be different using a 3510 or 4010. I would think the 2 speed in the 2510 may be jerky because its hard to find a good pace, either to slow or to fast for the job at hand. There are times i wish i went with the 2510, as it has a smaller footprint and would fit in my barn or down trail easier. But I figured the 2610 would be ok, even tho its big it can do more and is heavier built. As far as an 3510, i though about it long and hard, it was 2000 more than the 2610 and i thought about it hard and decided if i needed more horse power i would buy an old allis chalmers or massey to do baler work or something in future. As most my loader work , is easily done with the 2610. I couldnt suggest the 4010, not that its not a good tractor. But it is same motor from 3510 just tuned. and if I wanted 40 horse or needed the power i would have got a dk4510 as it would be better equipped to handle the power loads.