Well, because i have a Xentry / Star DAS System with SD Connect Muxer and full devmode i can tell you that Durametric can't do a fraction of what the MB system can do. If you want to have something comparable you'll need to have an unlocked PIWIS system.
Durametric can read and clear Porsche codes. It can data log. When it comes to programming there is nothing like PIWIS.
Also functionality of Durametric depends on the car you connect to. And the 986 is not comparable to modern cars where you can modify, calibrate or configurate nearly everything. So in the end the question is what you really need and what you can afford. PIWIS systems are much more expensive compared to MB diagnostic systems – even clones.
Just check the Durametric website:
Diagnostic Tool for Porsche | Durametric
Regards, Markus