domain name dash seo

I'm going to be selling niche products in a very competitive eCommerce market. I got the keyword with a dash... Ex.: dog-supplies.net Ex. Say the keyword is Dog supplies with a 3000 exact match in Google keyword tool. Is this going to be a good domain for me? Thanks for your replies. Would...

For example is it better if the domain contains two words but needs to be separated by a dash? Or is it better when it contains three words but no dash? Which one do you think is more user friendly and which one is more search engine friendly?