If you expect it through search engine then of course the hyphen. I would not even be thinking about it if these are good keywords, I would have already bought it.
I picked up www.keyword1-keyword2.com (under construction) without even thinking about whether the un-hyphenated .net was available. (I haven't even looked but I will look now).
However, the hyphenated .net and .org are apparently equal to the hyphenated .com in google anyway.
[edited by: Woz at 5:34 am (utc) on Jan. 29, 2003]
[edit reason] TOS#13 [/edit]
I have been thinking about my last post above and I should add the warning that google might change the way it processes URLs, then the hyphenated name might not be as good as the un-hyphenated.
This is unlikely but it is just to give you an idea that there is no perfect solution. You have to balance a number of different variables that relate to different aspects of your business. Then you choose the best or better solution from this, not the perfect solution.