They are fairly similar in quality. When I was evaluating them, on average, I was having more choppiness issues with Skype than Gizmo so now I use Gizmo predominantly.

I have found that with some public networks one is blocked while the other works fine. It is not one that is consistently blocked though. Either way, the blocking APs are in the vast minority. But if you run into one, download the other client and try it out. The beauty is that you don't have to use one *or* the other.

The good thing about Gizmo is that it uses the standard SIP protocol so the recent software built into the tablet (rtcomm), which has SIP support, operates with it just fine and you don't have to install anything.

With the proprietary Skype protocol, you must use their client.