Nice truck.
I don't know how this changed into a clutch/trans thread, but my choice is auto. I have had many manual transmissions, and few autos. I always thought a manual was more fun, but I guess I am starting to get lazy at age 38.
As to holding a vehicle on a steep hill by partially releasing the clutch, are you talking about the second or two of slip while engaging or the entire red light? It is absolutely fine to slip the clutch a little to get going from a stop on a hill, but absolutely not fine to hold the vehicle from rolling backwards on a hill during a red light.
A normal start slips the clutch for about 1/2 second. At very least, the wear would from slipping the clutch for 35 seconds would be equal to about 70 normal starts. This would, by definition, be accelerated wear. The other problem associated with this practice is heat, which will cause glazing and hot spots, reducing the overall gripping power of the clutch.
An automatic uses sets of thinner friction plates and bands with the same type of friction material. These are held clamped , while engaged, by hydraulic pressure. When the automatic transmission is working properly, there is very little slippage of these parts. The firmness of the shift is dictated by the hydraulic valving. If these parts are allowed to slip too much, the tranny isn't long for this world.
The torque converter is fluid driven, and there is slippage there, unless it is a lockup torque converter, which in effect provides a solid link between engine and transmission like a manual clutch does.