if you dont need breaks then generally a one way is faster than a spool(locked diff)..
the one way allows for the front tires to rotate at different speeds off power going into the corner and since the outer tire is traveling a farther distance through the corner than the inner tire, this is the fastest option, whereas the spool doesnt allow for the tires to rotate at different speeds, and this creates friction in the corner, scrubbing speed..
so.. a one way is faster but harder to drive and the spool isnt as fast but is easier to control..
I prefer to experiment until I find the right weight oil for the front diff.. that way I still have control and dont scrubb as much speed as a spool would..
I hope that made sense..