If it's humbuckers, always bridge. Especially with fast material there's just so much more focus and definition to the low end.
I had a long conversation with a real bass expert who runs a high-end bass shop here in Leamington and he said that he found that the better the playing, the bass, the amp and the cab all were, the less he ever uses a blend of pickups. After testing out a variety of equipment in his shop I'm inclined to agree.