Logic Studio or just Pro

I'm deciding whether to get Logic Pro or the entire Logic Studio Package:

Three questions:

Are there more instruments and sounds in the Logic Studio package, as opposed to just Logic Pro? This is not made clear in the descriptions.

What is the advantage of having Soundtrack Pro to work with along with Logic Pro? I don't find any description of what Soundtack Pro is or why it is advantageous to have with Logic Pro.

What is WaveBurner? Is it apart of Logic Pro or only in the Studio package. Is it a component of the MainStage product? Does it have a use apart from the MainStage performance use or only in conjunction MainStage performance use?

Thanks,

James