i think matt cutts from google said that hyphens are better, try searching hyphens in DP search and u mite find the thread i saw it in
HYPHENS! Google ignores underscores. It is not considered as a divider by Google. Hyphens are seo friendly because Google consider them as the best divider for the body text and URLs.
I've seen it posted many times that the common wisdom is as JessieJames27 has already posted above. If I can use an example from the above signature - http://www.example.com/luxury-homes-for-sale.html - is interpreted for the keyword phrase "luxury homes for sale" whereas - http://www.example.com/luxury_homes_for_sale.html - is interpreted for "luxuryhomesforsale" which is not going to be quite so helpful. Given the choice, I'd use Hyphens every time.
For search engines, it's irrelivant. For users, it can give a spammy impression, and is more annoying to type in / hard to remember the URL.
hypens is better for google as it treats it as a space and consider it used to join two different words.. i mean that's what i read somewhere
i made website for SEO certified guy. he said me first go with hyphens and later he told me to change on underscore. is hyphens is good then why he told me to change on underscore, i am confused from that days which one is better. the guy is certified from Australia. i also need help on this topic. thanks
As Matt Cutts has recommend dashes instead underscore in 2005 as detail information is mention in the given link http://www.mattcutts.com/blog/dashes-vs-underscores/ In 2007 matt as mention in one of the interview "Underscores are now word separators, proclaims Google" http://news.cnet.com/8301-10784_3-9748779-7.html still Googlebot couldn't "see" the words Rajasthan or Tour. Instead it read Rajathan_Tour as one word. we can take example Rajasthan_tours Rajasthan-tours