My gut instinct tells me to choose the one utilizing the .com/exact-match/
This coming from a customer perspective. When I search for Diving Equipment I'm going to want the phrase, or something similar, in the url. Of course, both of these match that idea. However, the second one allows me to read it as one piece, and my subconscious is more likely to perceive the page as such.
As for the search engines. Using the latter one will give a more clarified answer to what this page is about without additional context. The only point where I would see it being too complicated is from the length of the url; especially with blog posts.
http://www.dive.com/blog/The-Absolute-10-best-scuba-diving-accessories-in-2011/
*That being said, I have no documented proof of such, and have never seen a case study for it. It's just simply my interpretation.


(Actually much lower because of Title and Body being counted separately)