Best plugin to redirect OLD urls to NEW ones ???

Hi,
I have a few pages on my site that use bad urls, i would like to change the slug of these posts so the url becomes more seo friendly.

For example :
send old url : http://www.mysite.com/category/slugofthepostthatidontlike
to new url : http://www.mysite.com/category/new-slug-more-seo-friendly

I know there are many ways to do redirections, and i know there are many plugins… However I would like to know what is the best plugin that will do this for me ? Best would be defined by the plugin that uses the most efficient methods (seo friendly, keeping PR etc) and is the easiest to manage.

Thanks !