As I understand it, the main difference is that the Falcon rockets are (or are eventually meant to be) much less dependent on refurbishment between launches. The Space Shuttle required extensive and expensive work between launches to the extent that many critics[1] claimed that it wasn't truly "reusable". (IMHO, while the shuttle program definitely didn't achieve its goals, it seems like calling it "reusable" is fair).

As for gliding back: the Falcon booster does not actually achieve orbit-- when the main engine cuts off, it is on a ballistic trajectory back to the ocean. While it may be possible to design some sort of gliding apparatus to "save" a booster on a sub-orbital trajectory, it is (again, as I understand it), much simpler to simply adjust that trajectory via a boostback burn that reverses or slows that trajectory, and to then perform a suicide burn[2] to recover the stage, either on a barge or (on lower orbit missions) back on a land-based pad.

I am not a rocket scientist, nor do I have experience in the space industry-- these thoughts are just based on what I've read following the SpaceX reusability program as closely as I can for the past few years.

I do play a lot of Kerbal Space Program, though.

[1] https://en.wikipedia.org/wiki/Criticism_of_the_Space_Shuttle...

[2] http://space.stackexchange.com/questions/10307/what-is-a-sui...