Chair style or DEX or regular inversion... What's the difference?

I was looking over the info & inversion sounds helpful for back pain. I noticed there are the DEX type decompression machines, chair type inversion machines & the regular kinds.

What's the difference between them in regards to what it does with the body?

How about this therapy - Muscle Balance Therapy™? Is this a scam?
http://www.losethebackpain.com/treatments/


Are other brands better or worse than the Teeter brand? Seems many people here are into the Teeter one. Is there any marketing going on here or is it really the superior brand?