Answer:
If you're talking about the Google Toolbar pagerank, there isn't a difference at all in that Google's toolbar will give you the same PageRank data as if you were to search by any other method.
I haven't heard of any other toolbar pagerank. There is a very cool SEO tool that works well with Google's search results that will not only show you how many incoming links a specific page has, but will also show you the PageRank of each page in the search engine results.
http://tools.seobook.com/seo-toolbar/
http://www.coae.net/textlinks