I think that the Extension of pages do not matter: the real thing is content of the page matters. You just need to make sure that the URL of your site do not create duplicate content problem and that there are not too many parameters in the URL is you are using PHP, .ASP etc
Do you mean which is the best out of .asp or .html? The extension doesn't matter, it's the page content and links that count.
If your talking about for the purpose of ranking in the search engines, I dont think either are better than each other, they would both be treated the same. As people have mentioned, it depends on the number fo backlinks and trust of your site.
Years ago CGI-BIN was thought to take over the web now look at it. I say no extension is always to best as it will keep up with the changing times. Look at wikipedia. But for the time being .html is good for friendly links and php for dynamic links. You don't want to have article.html?t=100 and the-best-article-ever.php
It depends on what context first. If the context is programming then php is the best, if the context is SEO then html will be best because it's search engine friendly. You can program with php and use html for the output for the best result.
They've had an official blog that says url rewriting isn't needed any longer, as far as Goodle indexing is concerned. It may make a difference to Bing, though.
i do't think any of them is better, just do url writing and remove .html and .php, .asp extension that will be more better.