I've just had the opportunity to compare voice quality with back-to-back calls on GSM, JabPhone and SkypeOut. JabPhone wins easily, but there are provisos.
First, the test:
- Calling from Sweden to a fixed line in Johannesburg, South Africa
- Three calls, GSM, JabPhone and SkypeOut
- The latter two on a well spec’d machine connected to a 2Mbit frame relay (not loaded)
- Best voice quality was certainly JabPhone, according to both parties (and I asked the receiver before expressing my potentially biased opinion :-)
- The GSM call was worst in basic voice quality, but did not suffer from the same time-lag and occasional moments of silence that both VoIP services had.
- Best price was certainly SkypeOut (who probably have a POP in Johannesburg, which I suspect JabPhone doesn't). Skype was about 30% the JabPhone price, which in turn was much cheaper than GSM.
- JabPhone killed the call with no warning when my credit ran out, which was a bit unprofessional (as are many aspects of the JabPhone service).
- Overall, all three were passable as voice calls, but none were great.
Because JabPhone has the best basic voice quality, I rank it best overall for longer term potential, since the remaining problems are all things that can presumably be addressed. The service is currently advertised as version 0.2, so I expect it will be much better by version 1.0.
Of course, it goes without saying that these opinions are entirely subjective. I’ve always found Skype voice quality to be a bit weird, even back in the days when I did not have the occasional ‘really-bad’ Skype calls (today’s was a good call). I know of others that disagree and find Skype to be great.
When all is said and done, although I have access to, and use, three different VoIP systems (jabber/GoogleTalk/JabPhone, Skype/SkypeOut and a SIP service with x-lite), I still use Skype the most. So, no matter what I think of the voice quality, the continued convenience and professionalism of the service still keeps them in the winning seat as a service (for now :-).
Next to test: compare some other systems like www.jajah.com and the standard SIP service I mentioned above