in terms of value and seo it depends on what the words are. typically no hyphen is worth more when selling based of domain name alone.
either way register both! lol
I would say that both can get great rankings when done right.
And each affects SEO differant...
no hypen, google sees as a better chance it's an official site for those search terms. Thus boosts your PR
With hypen google can read the keywords better in the url and will boost your SEO for that.
it's kinda like 6 of one half a dozen of the other.
