Sgt_Kickaxe - 4:20 am on Nov 24, 2012 (gmt 0)
Minimal number of characters used in conveying the exact keyword(s) between the four options provided for pagename. I'd suggest using a hyphen between words but that wasn't one of the four options.
I still prefer .html extensions on pages I am unlikely to need to update and that don't have dynamic content. A quick php_copy gives me a static .html copy that my server gives precedence to automatically without any redirecting in htaccess, it doesn't get much easier (or faster) than that.
It's all preference, search engines understand them all just fine and there are better places to make gains with your SEO efforts.