Hi, I'm insterested in buying a license and have a question.
What is the main difference between xdebug vs PhpED's PHP Debugger?
What advantage does PhpED's PHP Debugger has?

thanks!

A few quick advantages of PhpED debugger:

PhpED is more stable than Xdebug.
PhpED allows you to set next statement to execute (to rerun or skip code during a debug session). For me, this is the main reason I choose PhpED debugger.
You can examine variables right the way through the call stack after a breakpoint.
It is non-intrusive to the web page; whilst PhpED provides information relating to the debug session, Xdebug outputs some information to the web page.

right, these four are the most important, but I'd also add some more:
-better performance (it uses optimized protocol, not soap-alike XML exchange)
-global breakpoints (a condition evaluated on each executed line)
-encrypted channel (special ssl-ed version of debug modules)
-support for IPv6
-IP-based security
-actively maintained (we support it and fix problem fast enough)

Now that the Xdebug 2.2.3 is out, is this still the case? Just curious...
Also any highlight for the new v11 debugger? Any improvement or enhancement on the debugger part? Thanks!

And it would also be interesting to know what the difference is between the phpEd and Zend debuggers?

You can check what's new in xdebug 2.2.3 on their web site. As far as I see it does not offer any new features, only bugfixes.
In general I don't see a point why it would be interesting to use 3rd party debuggers.
Plugnplay desribed why, I added even more reasons, and they all are still in effect.