Which are better, Knights or Bishops? I have always thought Bishops were better - I know that a KBB vs. K endgame is easily won, whereas KNB vs. K is difficult, and KNN vs. K is impossible; but then again, some people prefer Knights.  I realize there is a reason for each receiving the same point value (3) - they are so similar in strength, the Bishop on open lines and the Knight in close quarters.  

But is there any concrete study on the point, such as someone analyzing thousands of games in which one player began the game with two Bishops and no Knights, and the other had two Knights and no Bishops?
It depends on the board position. Both have equal points. But in a closed position, i.e, when the mobility of our pieces are blocked by the opponents pieces, knights have advantage. On more open board positions, bishops have advantage.