Originally posted by ChessJesterWhilst true that Bs work better on open diagonals if is frequently possible to make a B "bad" by fixing its pawn on the same colour (note you want his pawns on the same colour as his B not your pawns) but the ability of stronger players to come up with devastating N tactics can be awesome and unlike Bs a N can attack every square on the board so in the right hands a N will frequently be far better than a B in the latter stages of a game.
And, the bishop is percieved to be worth slightly more because most chess players tend to favor open games where tactics are more prevalent.
Of course a P & B can offer mutual protection that cannot happen with a N but a B may also be unable to cover the key Q-ing square.
Enter into this exchange with caution and ensure the position arising afterwards is favorable no matter which way around you do it.
Id have to agree that bishops and knights are really depending on the situation. But there is also personal preference. "Beauty is in the eye of the beholder" after all. personally, im a big fan of knights more so then bishops. I was a frequent player of ruy lopez, and so based my game around knights. The flexibility, ability to escape, and larger amount of squares to attack comes in handy for me. I think that against me, someone would have to worry more about knights then bishops.
There is also completely different styles of playing bishops and knights. I tend to just use bishops for attacking anything close to the king and setting up checkmates. Knights I find are better for capturing, using their ability of moving and getting out nice and neat to get those few pawns or the occasional stronger peice, and getting away with it.
Overall though, I have to say that the strengths and weaknesses of both pieces balance nicely. They have just different ways of getting the job done