The old 1/2, 3/4 & 1 ton references have little to do with actual payload.
True, they each have GVWR's, but with all the cab, wheelbase and engine configurations available, you have 20 different payload capacities per truck line.
As far as the F250 and the F250 SD, they are as similar as a Ford to a Dodge: 2 completely different trucks built on 2 different assembly lines. About the only major component in common is the 5.4V8 (largest available engine on the F250 and smallest available engine on the F250 SD)
Both models have their advantages, but for the lawn care/snowplower, the Super Duty would be the truck of choice. (And plan on carrying more than 1,500lbs with it.)