How different were Elizabethan wedding dresses than wedding dresses today?

Extremely different, as fashion and undergarments then were different. It also greatly depended on your station in life as to what you were wearing, as even the fabric told a great deal about you. Firstly, Elizabethan gowns were not white, but were generally your best dress. Most Elizabethan dresses consisted of bloomers, a chemise, farthingale, and a corset. On top of these would be the petticoat, the underskirt (the decorated front panel), the over skirt, a bodice and sleeves. Sleeves and underskirts were decorated and interchangeable. More information can be found here at elizabethan.org/compendium/62.html