I'll Butterfly Along with You

I just joined this KAL and am excited to start this. I managed to pick up some Kid Silk Haze & Rowan #37 from a LYS that is sadly going out of business. I've knit with KSH before, so I know it's going to be a slow project, but the finished result is worth it!

I was originally going to make the vest, but I was wondering how many balls of KSH I would actually need. The pattern indicates 3, but I've been reading that it's taken less than 2 for what looks like is the same length. For those of you that have made it with KSH or planning on making it, how much yarn did you get?

I'm also looking at making the dress instead... To bead or not to bead...

Decisions, decisions...

Any feedback would be greatly appreciated.