Dan,
The primary job of a hood is to shield the front element from stray light that may otherwise cause flaring, internal reflections and ghost images. As long as the hood achieves this, I can't really see what difference the material makes. I don't usually use hoods, not even on my bigger lenses. If I've needed to stop flare or other effects I usually get my wife to stand in an appropriate place and block the light. Failing this, I've improvised "hoods" from bits of paper and card that I happen to have on me.
Duncan
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