It is like someone asked somebody what time it was and then everybody explained how to build a clock! I don't care how the underlaid technology works! It is important that the product is well tested before releasing to the market and therefore Sorenson has been developing the nTouch vp from scratch for deaf people while ZVRS bought Z20 product off the shelf from Cisco.
To use an example that hopefully lights a bulb in your head, I'd rather watch HBO channel with reasonable video quality because of awesome movies, rather than watch a crappy channel full of terrible B-grade or even C-grade movies.
This is why I will not use Sorenson service, doesn't matter if they have great video quality, their terps are f'n terrible. I'm content with using anything that is non-Sorenson like SnapVRS, Convo, ZVRS, etc. Much better interpreter quality elsewhere.
This is my opinion.