F/O's taxying...
I've been in the LHS and the RHS on both single and dual tiller aircraft.
Gimme a dual tiller anyday... Simply because in a single tiller aircraft, the F/O will practically never complete a landing - Control is handed across prior to any taxiway thus the last fine part of braking judgement never occurs - And, the handover is sometimes an awkward moment!
Single tiller prevents F/O's refining their taxi technique, particularly on a longer aircraft in turns. For those Capt's who say 'but I know where I am going'. I have found, over quite a few years that the F/O's do too and mistakes (hey real world right!) occur in similar proportions!
And lastly, when my ticker ticks less than it should, my F/O is gonna get me to medical attention quicker...Gawd bless them....