Advantages of plastic miniatures:
-No pinning
-Plastic cement welds pieces together
-Lighter, allowing for more dynamic sculpts
-Paint is much less likely to chip
-Way easier to clean mold lines, convert, etc.
Advantages of metal miniatures:
-Can be traded or sold to obtain superior plastic miniatures
I love plastic, and Wyrd raised the bar with theirs, which are the best plastics I've ever seen (and the reason I'm getting back in!). So, I've thrown in my opinion.