what color bishop (light or dark), is more important for both white and black ?

hi friends!

1) what color bishop (light squared or dark squared), is more important for both white and black ? (both sides are equal).

i.e. a) what should white retain among light squared or dark squared bishop ?

b) similarly, what should black retain among light squared or dark squared bishop ?

please give your opinion and justification.

thanks.

It depends simply on the position and the centre.

is any general rule of importance applicable, if either light or dark bishop has to be choosen, when the game condition is equal ?

thanks.

basically its better to retain the bishop of same color as we are plying acc to me wow

There is no general rule for what you ask.  It simply depends on the current position, and to a lesser exent on the opening played.

In many openings Black has trouble getting good use out of his light bishop, but to be honest you have to be playing to a fair standard before this matters. Both sides King's Bishops (White's light and Black's dark) are on the same colour that the enemy King will go to when he castles, which can make the KB a valuable attacking weapon -- supposedly Tarrasch used to swear by it. But so far as that goes, see the first sentence again.

The problem piece for me is always the light sqaure bishop with black. So as black I am happy to exchange it (but its hard to force exchange). But it is only due to the opening I like to play.

In the very beginning, the white squared bishop for white, and the dark squared bishop for black, because they can attack the f2/f7 weakness.
But there is no general rule. Depends on the position, what weaknesses each side has, what the pawn structure is in the centre. 

Depends on the pawn structure and the dynamic aspects of the position