which is a better colour match?

The MM enamel and acryl are the same colours, so I think I'll go with that. The Tamiya one looks a little too dark..

Some of the Xtracolor RAL colors are wrong. RAL redesignated some of the colors in the 1950's. The Panzer grey is accurate.

Panzer grey is really dark, but the shade doesn't really matter that much since you need to do shading and hilighting to get a realistic effect. Testors Model Masters Enamel Panzer Grey is very accurate. I dont' know how close the acryl color is, but Tamiya's German Grey is close.

When it comes to german armor there is only one that works for me and that is Xtracolor's X800 RAL 7021 Schwartzgrau or panzer grey. Xtracolor make all the german colors and they are a copy of the real thing. Infact you have to lighten it a bit to get the scale effect.