Manuals used to make sense when the only HD truck trans were 4 speeds. A stick was the only way to get the really deep low and the nice OD high.
Now with the 6, 8, 10 speed autos.... I say this with a bit of a tear..... there is no real advantage to a stick as these newer transmission have a huge range. You are literally always in the perfect gear at the perfect rpm.
If you want a stick, go for it. It certainly seems all the new technology and development is going into the autos.
The last thing I'll say is that even the Class 8 market. over the road trucks. are going automatic. Quite a statement from the "gear jammer" days.