Hmmmm tough call. I'd have to say Reign in Blood is what I consider the "best" album there but since you asked which we prefer, Black Album would be my favorite. Pantera, I love dearly, but I always thought of Vulgar as their worst one. Some truly amazing songs but then a lot of what felt like filler to me. It was the bridge between their softer early period and their heavy later period and I felt like they hit their stride better both before and after.