I use a lot of Badab Black.......and I mean A LOT of Badab - to the tune of 3 to 4 pots a month - why? Becuase I paint a lot of models and I have found the Badab to be a good, quick shade, which after highlighted, really deepens the basecoat that you are painting.
On the suggestion of a good buddy of mine - Luke - I picked up some of the Vallejo Model Color Black Shade, and did a side by side comparison with the Badab Black.
Here is a Starter Kit Marine, based in Cygnar Blue Base, Ironhull Grey, Boltgun metal, and Brassy Brass, and then washed with GW Badab Black.
Here is another Starter Kit Marine, same base colors, but washed with the VMC Black Shade.
Neither wash was thinned, as I normally paint these right out of the pot. So far they are about identical.
After bringing the base colors back up, they appear pretty similar.
GW Wash, re-highlighted.
VMC Wash, re-highlighted.
To me, close enough - Yay for saving cash.........And just in time too - I have a few vehicles and larger models to paint for the Wife's Necrons.