Hyphen in domain name (not the usual domain/hyphen question - ish!)

It's my first post, so - hello, and please be gentle!

My question is regarding the use of hyphens in domains - I've read just about everything that I can regarding multiple word domains and most people seem to have their own take on it, which is fine, although there seems be more people in the "non-hyphenated is better" camp.

This question is slightly different though, I plan to purchase a domain name for a word that is commonly hyphenated, even Google's exact keyword results indicate that the hyphenated version is searched for more than the non-hyphenated.

There are also big differences in Google's search results too, for the hyphenated (high exact searches) phrase there is about 189,000 results, and for the non-hyphenated (lower exact searches) phrase there is about 1,100,000 results!

What I am wondering is whether it would be better to purchase the hyphenated or non hyphenated version, given that the there are more exact keyword searches per month for the hyphenated one - but then would I rank better if I go for a non hyphenated version, which yields less exact keyword searches per month - or does it even matter?

I also intend for all of my traffic to be organic, so long-term branding of the domain will not an issue - I just want it to rank as best as it can.

Finally, if I purchased both domains, can anyone give any advise on how to basically benchmark, test and compare the ranking for each?

Thank you in advance, Nathan.

It's not too hard.

1 - Setup a simple (no wordpress, no nothing) website for each domain.
2 - Setup awstats, or any simple log analysis package.
3 - Write one article (600 words+). In plain html.
4 - Upload the same html file to both domains (as index.hmtl )
5 - Go to Ping-o-matic and ping (more-or-less at the same time) both domains at the same time.
6 - Wait for G***/YH**/Bi*g/etc to index your site.
7 - Take a look at your awstats.
8 - Profit !

Would I then not be penalised for duplicate content though?