I bought each of the Princess Leia costumes for sale on Amazon and this one is the winner.  The reasons:
1. It's a "traditional" Leia costume, basically a white robe with a mock turtle-neck collar, and a nice little hood attached to the back. It's just the right size, not too big when it's down, but big enough that when it's on it looks like Leia
2. Material is pretty hefty compared to some of the others
3. Arms flair but not too much

It comes with white boot covers that I can't imagine anyone wearing, the wig isn't great, and the belt is pretty cheap, so I ended up getting cheap white gogo boots and I'm going to make my own belt.  I also bought the Princess Leia headband&nbsp;<a data-hook="product-link-linked" class="a-link-normal" href="/Adult-Princess-Leia-Headband/dp/B003IISRXI/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Adult Princess Leia Headband</a>&nbsp;and some brown hairspray to make my own Leia hair.  So I ended up spending a lot on a Halloween costume, but I wanted it to be pretty authentic.

Here's a breakdown of the other two Leia costume options:

1. Star Wars Secret Wishes Princess Leia Costume by Rubie's Costume Co - a.k.a. the "Sexy Leia"
<a data-hook="product-link-linked" class="a-link-normal" href="/Star-Wars-Secret-Wishes-Princess-Leia-Costume/dp/B002JTX90I/ref=cm_cr_arp_d_rvw_txt?ie=UTF8">Star Wars Secret Wishes Princess Leia Costume</a>
Cheap material, two slits going up both thighs, the bottom half is tight, top half a little looser.  Sleeves are very flared.  You will have to wear something underneath, it's completely see-through.  But if you want to be sexy Leia this is your best option

2.  Star Wars Princess Leia Adult Costume by Rubie's - Traditional Leia costume
[...]
This is very similar to the one that I kept, but it's not the "deluxe" version.  The big difference is that this one does not have a hood on the dress, and no booty covers (which you wouldn't use anyways).  And the belt is a piece of cloth instead of the cheap plastic that comes with the other two.  So if price is most important to you then this is a good option for buying the basic Leia dress.

Hope this helps! And thank goodness for Amazon's return policy which let me do this research.