Calling them out

Should I call out a vendor who I don't think is quite up to snuff?

Definitely.

The way I see it is that a lot people are trying to make this the best day of their life. They are investing their time and energy to check out these vendors and meet with them, correspond with them, and listen to them sell. When vendors do something that is not well, then of course you don't go with them. But if they do something that is memorably not well, then i think you should spread the word so other people don't waste their time.

In due time I will be calling them out.

Caterers beware.