Here is what I have more-or-less learned about anti-seize as related to spark plug threads:
On aluminum heads, use aluminum-based anti-seize (sparingly on zinc-plated threads, a little more generously on non-plated threads). Although NGK recommends against using anti-seize on their plugs, I would probably do it anyway. Avoid using copper-based anti seize on aluminum heads since it can promote galvanic corrosion of the aluminum.
On iron heads, the use of metallic anti-seize is not typically recommended. I used copper-based anti-seize on iron heads for years, but I've since heard that can cause galvanic corrosion to the iron... I never had a problem though. The use of aluminum anti-seize on iron threads is not recommended because it will cause galvanic corrosion of the aluminum base itself and might make it more difficult to remove since the aluminum metal will have corroded into a white aluminum oxide.
Nickel anti-seize is uncommon on automotive applications since it is meant primarily for use on stainless steel.
I usually keep aluminum and copper anti-seize on hand but I find that I don't use the copper very often.
Take this for what it's worth, but I'm a chemist, not a metallurgist, so YMMV.