Tiller any time you can!!!!
The REAL difference is with a tiller you can sit up high on the coaming and with a well balanced helm you will be primarily pulling on the tiller (extension) mostly to keep course. Sitting on the coaming has the strategic advantage of being able to see the forward sails better. With a wheel, either you get your vision trapped by being down low or by the mast and if you try to sit on the coaming, the usual corrections are by 'pushing' the top of the wheel ... which is VERY tiring.
A tiller usually means a 'well balanced rudder' ....
With the sometimes HUGE forces generated by 'unbalanced' rudders, you NEED a wheel to overcome those forces.
Gimme a tiller (with a matched balanced rudder) any day of the week.