I voted 5 speed manual of course! like dieselcash said, nothing better than changing gears!
I try to DD in my 91 gasser. it gets great mpgs, is cheap to maintain, and has inexpensive 15 inch rubber. for a daily driver, the 5LM60 is a great transmission. nice even splits. first is high for towing, but it can be done with the surprising low end torque of the 4.3L v-6.
The NV4500s are better suited for trailer pulling, as the 3-4 shift is annoying when driving around, but 3rd is so much lower that it makes a great mountain pulling gear.
the SM465 is what it is in my 91. like the 6.2L that twists it, it isnt anything fast, but it is dead reliable.
everyone should have one manual transmission in their fleet IMHO, wheter its a car or truck. It just brings back simplicity, and it takes your mind off of things.