Thank you for the comments, everyone. Consider me a Philistine. I'd
never really given it much thought until I was eating vermicelli and
noticed it was a bit different from spaghetti :-) And from time to
time I'd wonder why use one pasta rather than another because, to my
way of thinking, as far as I could tell unless the package said
differently they are made from the same ingredients and had the same
taste.

And the comments about angel hair were also interesting because I
associate that more with Vietnamese dishes rather than Italian. And it
seems to me that vermicelli was more like what is offered at the
Mongolian restaurant near me.

Too bad the cooking shows, the ones I've seen, don't seem to round out
why one might choose one type over another.

I'll do my best to keep in mind your comments the next time I cook or
eat pasta :-)