John, you’re still looking at search terms, and going down the same incorrect path. It’s a leap of logic, or a “what if” scenario that amounts to nothing more than FUD. Just because Google acts in a certain manner when it perceives that human is searching for an underscore has absolutely no bearing on whether or not it does or doesn’t apply higher or lower rankings to content with - vs. _ in the URLs.
Derek, I think we are talking about two different things. You are talking about ranking and I am talking about how Google searches text.
However, you can’t rank at all for “Expression Engine” if your entire site uses references to Expression_Engine.” You could rank (somewhere) for “Expression Engine” if your entire site references Expression-Engine.” I am not saying you would rank better or worse depending on the term you use, but you have to use the correct term to rank at all.
As you can see from searches, your URL is used for finding search results along with the rest of the content of your site. So the URL is content. Some sites (picture, video or Flash heavy for example) can use all the content help they can get. You might as well use a URL that helps you. In this case, for Google you should use the dash.
