it really depends on where you are at...running a wide pattern with cards/hypers can put you outside the stack so to speak for one mic and dead on with the other...I would agree though that any stereo pattern (outside of XY) makes for a much more natural tape when stack taping than just pointing the mics at the stacks....it allosw the mics to have some rejection, which gives it a better sound imo.
I have heard some really nice omni stack tapes (not many out there though), but for the msot part, I would say cards, and run a pattern, usually DIN up close, and if you are a bit farther back, NOS and ORTF can work...just pay attention to where you are and the way the stack is situated....