Magic Mask - more effective for green or white background?

I aim to video a talking head person (with plenty of arm movements) filmed against a solid background under studio lighting, with the aim of using Magic Mask to mask the person.

Would "Magic Mask" be more effective when the person is against a pure white or green screen?

Person has dark colored hair, so I'm guessing it might stand out better against a pure white backdrop rather than a green screen?

I'm asking so that I can buy the recommended colored backdrop.

Why do you want to do magic mask if you can control the background? Do a greensceen key and get 10x more detail. Magic mask is the last resort if you can’t key, not first thing to grab. It is slow and has low quality.

I thought the same as Hendrik.

Yeah, the purpose of magic mask is to isolate a subject from an unprepared background - and even there it often needs a lot of care and attention to get it looking good. If you can control the background, use a green screen and isolate the subject in post production with a chroma key mask - it's way faster and it'll give much better results.

A green screen is better than white because it's easier to isolate a pure colour (as long as the subject isn't wearing anything green). With a white background you'll tend to catch bright parts of the subject (highlights in the eyes, white patterns on clothing, etc.) in the mask, which will take additional garbage mattes to deal with.