Congrats on finding a dress you're all happy with (and that you might be able to use again)!
When I was married in September 2006 I picked the color and let each girl pick the style they liked the best. Actually, that's not 100% true - I picked a color, and my sister (who was also my Best Lady - she refused to be called "maid" of honor) decided a different color looked better on her and asked me to change
It all worked well though, I ended up liking the color she picked better - plus I can use it for leverage when she gets married.
It did work out well though, each girl was able to pick a dress they were comfortable and felt good in.
I've seen lots of wedding though where the maid of honor's dress is a different color or shade than the bridesmaids' dresses.