Rhinestone Studded Charmeuse or Green Washed Silk?

So I officially got asked to prom, and in the cutest way too, but i don't want the traditional prom dress...you know cleavage down to there, plunging back, rhinestones, tacky shiny bright fabrics..prom in my school is much different most girls wear nice dresses, no one goes around searching for prom dresses in my school we go looking for evening dresses, but most of the time everyone shows up with the same kind of dress or style so this year (im a junior) i can experiment with color and print unlike next year when i become a senior and can only wear white or beige so I saw this gorgeous DVF Maui Maxi Dress in a gorgeous green at Saks, it was like six sizes too big but the color was gorgeous against my tan complexion but then i saw the same style with more color on the internet...so i'm in a rut, i've yet to try the second one on but there both in a gorgeous washed silk fabric. Now if it was up to me and money or color was no object then i would definitely get this Matthew Williamson dress that's about $1,000 on Net-a-Porter but its always fun to look at

Shopbop.com
Saks.com

Netaporter.com