ScriptManager, RadScriptManager, ResourceLinks, JQuery, User

1) Why is there a scriptManager and a RadScriptManager, any benefits, any reason to use RadSCriptManager at all?
2) Sitefinity also has a ResourceLinks control. Now exactly which one is better to use? ScriptManager, RadScriptManager or ResourceLinks? If you load Jquery using the Resourcelinks control, but you have a ScriptManager on the Master page as well is the JQuery file going to load more than once?
3) I have a ScriptManagerProxy control loading a bunch of script files in a user control, but they're loading before the JQuery file output by Sitefinity.... how do I get it be in the correct order?

Edit: I tried removing the ScriptManager from the page and using only the ResourceLinks control. This throws an exception saying that a ScriptManager is required on the page.

So now I'm using ResourceLinks to load one version of JQuery early enough and ScriptManager is loading another version altogether.