Hi Mark
VDI/VDE 2617 and CMMA (more or less a reduced version of VDI/VDE) are outdated. They are still used by some manufacturers because they are manufacturer friendly.
For example the small print in VDI/VDE says that you have to accept the CMM if 95% of the results meet the specs. It means 5% of all your results can be out of spec, but the CMM is considered ok.
Manufacturers also like the old VDI/VDE standard because it makes the their numbers look very good. For example the form error of the CMM is not specified. Instead you get a V2/V3 spec, which is in fact less than half of the CMM's real form error.

Much more customer friendly is the ISO 10 360-2 standard.
It specifies the CMM's volumetric length measuring error E and the CMM's form error R.
The tests and the evaluation are straight forward, so every operator can repeat these tests.

If your CMM comes with a rotary table or can do scanning, then look for the following:
ISO 10 360-3 (Draft) deals with CMM's using a rotary table.
ISO 10 360-4 (Draft) describes the CMM's form error during scanning.
ISO 10 360-5 (Draft) describes the CMM's error when using multiple tips.

You can get these standards under following address:
http://www.din.de/beuth

Request all the CMM makers to provide you with specifications according ISO 10 360-2. Only then you can compare the specs of different CMM's.

Regards
Juergen Roos