Pretty much anything good is going to be PC-based. All the manufacturer scan tools are now (and have been).
For what a good scan tool would cost, you could buy VCDS, buy a brand new PC, and still be way ahead.
VCDS will just do the generic stuff on the MB products, which will be limited to engine/transmission.
We also have one of the Autel scan tools here, the full bundle Pro version (it was about $3500). Even it won't work as well as VCDS does on a VAG product, and on top of that, after two years you have to pay to keep it updated. And while it isn't a Windows-based PC, it is an Android OS, like a lot of cell phones. Essentially a tablet PC.