Unique gets my vote everytime. A little tricky to meter consistently but it's a great all around pistol powder.
Look around from some Alliant HERCO. It's as versatile as Unique, and a little slower burning, so you'll get more of the "top end" of the .44 Mag with it. Like Unique, it DOES burn a little dirty, and sometimes "meters like cornflakes", but I often find it left over when all the Unique's been bought up.