Payne’s grey as universal shadow—ink or acrylic?

I just watched Vince's video on Universal Shadows Colors. He uses Daler-Rowney FW Ink, Paynes Grey.

At the art supply store, I'm finding a number of acrylics too: * Golden SoFlat Paynes Grey * Liquitex Basics Acrylic Fluid Paint * Liquitex Soft Body Artist Acrylics Plus Pro Acryl

Given the above, is there any reason to go with the ink or one of the acrylics?

On another note, are there other uses for the FW ink besides mixing with your base for shadows and branding?