Green or black cardamom and why?

The black has a deep, rich smoky quality . . . better suited to savory dishes than sweet, in my opinion. ;o)

I've only seen Persian cooks use green cardamom. My cousin Mahin, who showed me how to make nan-e panjere'i, aka deep-fried "window cookies" with cardamom, actually cracks the green pods, extracts the seeds, and then grinds them for use in each recipe - wow! I'd like to try the black cardamom some time.