OP, when comparing spec sheets for lifting at ground level, and breakout forces, one of the reasons that this will be difficult to do is that SS and tractor loaders use different geometry for lifting. Independent of whether the cylinders are larger, you can see in SS geometry that the load stays close to level, even as the load is lifted. That is not true with a tractor. If you did not curl forward as you lifted, your load would be facing nearly vertical on many tractor loaders at full height, and the longer the arc would be that the load needed to travel. So the longer the load gets (i.e. pallets vs loaded bucket), the more the tractor capacity will drop, because the load needs to travel further to complete the lifting arc. So that's why there's some examples of the Kubota SS lifting a pallet when a comparable (on paper) kubota TLB won't do it. It's more complicated than hooking a gauge to the lift pins at ground level and reading what it says. In the real world you generally lift forward of the lift pins, and the further forward you go, the lower your capacity will be. This is more pronounced with tractor geometry.
Regardless of all that - I would look more at overall operating weight and use cases. My neighbor has a New Holland LX665 that I borrow sometimes, and I have a 50 HP tractor that weighs about the same. The lift for a bucket full of material is probably about the same. My tractor when I have heavy counterweight is much more stable, especially over rough terrain. I can get out of the tractor safely with a suspended load. The tractor is less maneuverable, and you can't see the bucket edge. The SS is better at grading both due to visibility and to lift arm stops. I can run a mower on my tractor at the same time I have a grapple attached. The SS has terrible ground clearance and is prone to getting stuck in the mud. The SS is shorter and can be moved on a smaller trailer. The tractor does 13 MPH on the road, where the SS probably does about 5. I can pull a trailer with my tractor. As has been said, implements are cheaper with the tractor.
There are a lot of areas of overlap, but a lot of differences also. For my uses, I greatly prefer the tractor. If I was working in the dirt all the time, I'd probably have a SS. For material handling that you need to get out of the machine with a suspended load, as others have said - the only SS that you can do that safely is a volvo or JCB. Don't get out of a SS under a suspended load.
