To cover the first paragraph. My advice would be have a listen to some of the music being put out in the user submissions forum, by people using BIAB, many of them solely using BIAB. You'll be surprised about how good it is.

The musical styles you list are just a few of the categories available, and then there are sub-categories on these. So it would easily cover them.

And to the specific questions:

1) Not sure because I don't know the other solutions you named
2) No. It's not limiting at all. But it can cost, but then again, you pay for good quality! And some of the realtracks are played by top class musicians for BIAB so they're better than you'd find anywhere.
3) Yes
4) I think the windows version allows loops so I guess so, I use the MAC version so there are a few features only available in the Windows edition.

Well, thats my take on it.

Hope it helps a little
Greg