In mount&blade warband, you can manipulate your chance of deploying your desired type of troop by simply move them up in the party screen.
Example: If you want to archer duel with the castle/town you are sieging, just move up your archer units to the topmost position possible in your party.
Put the archer at the bottom
In-game result
VS
Put the archer at the top
In-game result
P.S. You can press backspace during battle to see the UI in the images.