precisely. listen and decide.

from experience listening to friend's setup, the bi/dipolar are kindda vague sounding. you won't get the accuracy of monopolar.
accuracy like at the scene in avatar where the wolves are circling the hero. you won't get the feeling that the wolf is circling at your back moving from left to right and front to back.

IMHO some movies are mixed so that the surrounds produce surround sound (sound from the back) (like avatar) and some are mixed so that the surround produce ambient sound (like kungfu panda). when playing avatar with monopolar surround, you're better off using monopolar and get the accuracy. but when playing titles mixed with ambient sound, IMO you're better off using bipolar/dipolar.
kungfu panda sound kindda strange with the sound of rubble dropping from the back (on monopolar) when it's supposed to be dropping from the center. well at least on my setup. but avatar sounds pretty amazing with the wolves circling all over you.

and another thing to consider, with monopolar you're gonna get overpowering sound either from the left or right if you sit off centre. one channel is gonna be louder than the other. with bipolar this effect is more forgiving because it sounds vague from the start haha

just my opinion. and opinion varies

yes, but with less accuracy.

in my system you could hear depth even from the surround speaker. like in the intro of sherlock holmes, the horse carriage sounds like it's coming from a distance from your back then move passes you and goes to the front. gives me goosebumps haha.
when properly configured, there's not just left, right, front and back. there's also depth. the accuracy of monopole extends this depth for the back speaker. that's what i really like about using monopole for surround.

might not be your cup of tea though.

my hall is attached to the dining area. too far out to put the surround at the rear. so i mount it on the side wall, 10-20 degrees behind the listening position, 4 feet higher pointing downwards.

bro i'm not elite lah. elite are those people running higher end denons/onkyos/pioneer elite/marantz with XPA5.
i'm just peasant with entry level 5.1 setup.

kindda. it disperse sound in 3 different way.