Beauty Dish VS Ring Flash...

I've started to do headshots along with art/fashion photography. In everyones opinion which would be a better for my next purchase a Beauty Dish or Ring Flash? Both seem
very versatile and I'll most likely end up with both, but because of pre$ent finances I have to choose one or the other for now.

Just build you a beauty dish to use with your 580exII. I built one and it's very easy and cheap but very well put together. Love this design.
http://vimeo.com/95779​63

Regardless of the brand or if it's a DIY I would suggest getting a beauty dish before getting a ring flash. The ring flash is interesting and it's a nice effect once in a while but it's more of a specialty modifier that should be selectively and carefully used.

On the other hand you could build an entire style and portfolio with a beauty dish and you'll find it to be much more versatile as well as having the ability to modify the quality of light with deflectors, diffusion socks, grids etc.

BD and Ring Flash are specialty tools.
As Rob mentions, BD can be moded easier.
The Buff Ring Flash has some nice modifiers that make it into an Octi. Either as ring flash or as a stand light.

Thanks for the input! I'm leaning towards the Beauty Dish... The results posted with a grid and sock look great. My friend uses his RingFlash all the time, but all his shots look the same.