chrome tan is basically upholstery and clothing leather, soft and supple. It's next to impossible to tool it, edge it or burnish it, but it does make nice bags, jackets and even watch straps.
veg tan is tooling leather. It's what you want if you need to stamp, carve, edge and burnish your project. It gets more supple with use. A light weight veg makes good watch straps, too.