With current designs, Musks satellies need special ground stations to communicate with. They can't beam internet direct to your phone.

Loon can connect direct to your phone.

Both will require a fairly decent set of base stations so the balloon/satellite itself can connect to the internet.

That's hard to tell at this point.

From a pure physics standpoint, loon should be able to outperform satellites in urban areas and in receiver cost. I'm sceptical if that is enough to justify the project, but we don't know how Musk's satellites will perform yet

Arguably no, but lets see if Musks plans are more than PR speak to build up hype. Right now, Google is way ahead.