It's a long time since I used either, but in terms of functionality, the Nostromo is basically a mini-keyboard type of controller - you use your fingers on it.
The Strategic Commander has buttons too, but the whole thing is on a kind of short stalk [so it kinda floats above it's base] enabling you to shift and tilt the playing field in [for example] RTS games.
I was really keen to get these originally, but I never found time to learn how to use them properly, and my setup is too cramped at the moment to use either.