I like Sellier & Bellot, becasue the red lacquer line around the case mouth and bullet gives me a good visual mark to check for bullet setback in rounds that were chambered. Also, it's just about the least expensive ball ammo in my shop, and it's been 100% reliable in my guns.
That said, right now I have more UMC around than anything else. It's just so convenient to pick up a box or two every time I hit Walmart with the SO.