From what I understand, metal tweeters are sharper and more crisp. The silk tweeters are more natural and mello. I can't say much for dis. and adv. I'd go with silk if I got them.
often these are generalities of tweets. its more of how the tweeter is installed and how well tuned it is. you can definitely make a silk tweeter sound just as dynamic as a metal tweeter and you can get a metal tweeter sound as smoothe as a silk tweet. but thats IMO.