I have a set of Anthony Gallos (
www.roundsound.com), which the Orbs are based on. I can't find his name now, but the guy who started Orb Audio used to work with Anthony Gallo, and must have his name on some of the patents since Gallo hasn't sued.
I love the Gallos. They are great, even better if you get the wallflower stands as you really minimize reflections from nearby surfaces and diffraction from the speaker is really low due to the spherical design. Because of this the imaging can be really great.
Personally I would stick with Gallos, but I know a lot of people are happy with Orbs.
It is my understanding that the differences are that the Orbs are thinner in the metal cabinet, and I would guess that they don't have the S2 material. While on the Gallo site the information about S2 seems very market speak and snake oil it actually exists and has a positive effect. Basically it is polyolefin flakes that the speaker is filled with rather than normal damping material. Since the polyolefin is very dense it causes the speaker to couple with it in the lower ranges helping output, while high frequency content is unable to couple and is not enhanced.
Recently I listened to a bunch of the newer Gallo stuff, and all around I thought the A'Diva Tis sounded the best, but any of the Ti line sounds pretty good. The Micros are just a hair edgier than the A'Divas which are pretty darn smooth. Of course I also heard the Reference 3.1's which blew everything else out of the water, but I doubt you are looking for a $3000 set of floor standers at this point...