I am doing a 3 tier wedding cake. The bride wants smooth bright white icing-not fondant. There will be no decorations, she is adding ribbons and flowers. Which icing should I use-buttercream, italian meringue or swiss meringue?

Hi and Welcome to CC, Chattacake.

Decoding CC acronyms:

http://www.cakecentral.com/cake-decorating-ftopict-2926-.html

Everything you ever wanted to know about the meringue b/c's (and other frostings):

http://www.cakecentral.com/cake-decorating-ftopicp-6011626-.html

Everything you ever wanted to know about making your 1st tiered/stacked/layer cake:
(Has American b/c recipes and so much more.)

http://www.cakecentral.com/cake-decorating-ftopict-605188-.html

FYI, the meringue b/c's don't crust and require refrigeration. Also being made with eggs and butter the cost is greater than a shortening based frosting.

The crusting, shortening based American b/c's can be smoothed using several different techniques (see above thread) and are WHITE-WHITE.

Which frosting you choose is a personal taste preference limited by preferred smoothing method, refrigeration requirements and cost constraints.

HTH