Ohh good question .... i like knight i think that has more "versatility" and is capable to "JUMP" the block lines. but its hard to get checkmate with horse and other pice combined .
depends on the position. in a complex sicillian i like my knights combined with the black squared bishop. in a itallian or kings gambit i most prefere the bishop pair. but it realy depends on how the game wents how well your opponent is in tactics like forks and pins