Wall,
I can't imagine being able to control the tractor better than I can control mine with the hst. You can move a fraction of an inch when hooking up implements to the 3ph. Move at any desired speed while running an implement on the back at constant rpm, things like that, all without the need to move a shift lever. Not that shifting is a big deal. I think it is the low speed control where the HST shines.
On hills you can stop, back up, go forward, and so on and never, even for an instant, disconnect the engine from the drivetrain. You can change speeds on hills no shifting required...within the speed range you are operating in.
There are times when the manual shift tractors excel. For example, plowing, or doing other field work, where you want a constant speed. At least that is what I have come to believe by reading posts here. No experience on my part in that area.
On hills I personally keep thinking to myself, when I am changing direction, that I am glad I don't have a clutch to push in. When stopping with the hst, you have both the engine and the brakes holding you. [If you elect to push the brakes; generally you don't have to, as the hst will hold you.] Now if you are parking the tractor that is a different story, you would certainly set the brakes...on any tractor.
When changing directions you simply push the directional pedal in the opposite direction.
Now with some transmissions [gst I believe] the shifting sequence is automated and you don't have to do anything but select the gear you want, and the tractor does the rest for you. I have not driven one of these myself. I would imagine if you want to stop on a hill, you would have to shift to neutral, or push in the clutch. Plus push the brake. Certainly not a big deal. I just like having both the engine tied to the running gear at all times AND the brakes available too.
Like Rat advised...try both and you will get a better idea of how the HST compares to the manual shift. They are both good, depends on your needs and likes...There is no best tractor for everyone, just a best tractor for YOU.