When in conditions that cause us to use our rudders I'm guessing the 3% slowing caused by the rudder is more than made up for by not having to make corrective stokes.
It's interesting that most long distance paddlers use boats with rudders. Both round Australia trips were finished with boats that had rudders.
As I've said before for most of us rudder is a misnomer we use it more as a trim tab to keep our boats going straight when in quartering wind and waves. When I want to turn fast my rudder is up as I can turn a much sharper radius turn without it.
Sea Kayaker Magazine