Ideally, gaming wants all 5 channels to be exactly the same. They aren't doing any fancy mixing, they are simply positioning audio at 360 degrees and reducing down to X number of channels. As such, 5 matching speakers is ideal, that way a gunshot in any location sounds exactly the same regardless of which sound-hole it's coming out of.
Bi-poles's will diffuse the rear channels creating a wider area of coverage and larger sweetspot at the expense of locational accuracy.
Bi-poles were great for the ProLogic I days, but don't have much of a place in a modern home theater unless you are doing something odd like two-level seating or something.