Corset or Zipper

When it comes to your wedding dress, you'll encounter whether or not you want a corset or zipper back.  Of course everyone has their own preference, but there's some other little tid bits that you may want to consider other then the look.

Via Dress-Shop

Pros vs. Cons of Zipper Back
Whoever is helping you get into your beautiful gown the day of, the zipper is probably something your maid of honor or bridesmaids will most likely prefer.  It only takes 1 second to zip up your dress and whala you're ready to go.  The only drawback of having a zipper back is that your body needs to fit perfectly into the dress.  Zippers are definitely not as forgiving as corsets are.  You may need to make several alterations to make sure your upper body fits perfectly into the top part of your dress.  If you're a bride that is planning to lose a significant amount of weight, I would go with the corset just in case ;). 
 

Via EHow

Pros vs. Cons of Corset Back
The pros and cons of a corset back is pretty much the opposite of whatever the zipper back is.  Your maid of honor or bridesmaids most likely won't be too happy trying to get you into your dress.  It may take about a minute or so to get you into your dress.  Especially if you have a very fitted dress (like a mermaid) and you need to use the restroom.  That won't be fun.  On the other hand, with a corset there's less alterations you will have to worry about and it is very forgiving.  Plus, you can save money on alteration costs!  If you lose or gain any weight, the corset can help you fit into the dress perfectly without any alterations.