will pull the latest, non-minified version of the 1.x branch of jQuery from jQuery's own cdn.
This is currently v1.11.0
will pull in a minified version of jQuery v1.10.2 from Google's cdn.
Notice the missing http:// at the begining of the url.
This will cause things to break if you test locally, but has advantages when used on a server (namely the browser will use the page's protocol to try to obtain the file. On non-secure pages, http. On secure pages, https).
In your case I would use a specific, minified version.
Here is an interesting link on why it is best to include jQuery from Google's cdn: http://stackoverflow.com/questions/2180391/why-should-i-use-googles-cdn-for-jquery