Own domain with paid hosting is always the best where you have total control. Free blogger may be a good thing for starters but for established players, it may not be the better choice...
It all depends what your after, I dont think that either one is better than the other for adsense. I would say the best thing for adsense is a high pr and quality back links.
Own Domain as you have total control over it. You can modify, change, etc the theme or programming language of the page any time which u cant do in blogs. Also blog sites can disable your blog anytime whithout giving any reason.
It depends on how good you are at driving traffic, targeting keywords and getting ranked high in the Serps. If you're really, really good, then it doesn't matter where your content is located. (I can't argue with success - http://makemoneywithadsense.today.com/2009/03/18/how-to-get-blog-traffic/) If you're like most of us - buy your own site.
Depends on ur skill you can earn same from subdomain and free hosting. For direct traffic own domain is better.
For starters, like me, I go with Blogger (or other free domain). Its hassle free and all you worry about is the content.
one of my friend suggest to me to own domain and hosting for adsense approval.. so own domain is the best for adsense