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.
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.
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.