Question about "new" patch DK.

Hello, to start things off, i play a frost DK. I have not been on to pvp in a LON time, instead i was leveling an alt with a friend. Today i got back into it, i was doing some arenas (since i was already full malev) and the partner i was with told me to use blood presence instead of frost. I found the survivability much better, but the dps output was lower. I guess im asking, blood or frost presence for a frost DK?