Since most people are used to most domains not having a hyphen, "wordword" domains will always be the preferred option purely from a "typein from memory" perspective. But as far as a purely SEO/search engine generated traffic goes, either option is fine.
With the hyphenated domain you primarily run the risk of "traffic leakage" to the non-hyphenated version of a your domain (assuming you don't own it) from those that may have visited your site through a search engine and try to come back to it again (unsuccessfully) from memory. Your domain's keywords might be remembered, just not the hyphen that separates them.
Good luck which ever way you go!