<< Another reason not to use bipole - harder to wire. >>
Nope. I understand your logic though. Dipole surround speakers DO have two drivers or two sets (mid and tweet) facing opposite directions, but they are wired together, internally, out of phase. IOW, there's only one connection on the outside of the speaker itself, then inside the speaker, it branches off to the two drivers.
I have a set of Dipole surrounds myself...that's how I know.
Back to the question. It's pretty simple, actually. If your surrounds will be mounted in back of you (firing towards the back of your head) get monopoles. If the surrounds will be mounted to the sides of your head (firing at your ears) get dipoles.