My preference is a tiller. If my next vessel is sold with a wheel, I'll consider the expense of converting to a tiller, such is the strength of my desire for a tiller. However, the twin wheels are a different breed altogether, and this appeals to me. Therefore my personal preference is:
2. twin wheel
3. single wheel, (& as Cesar Milan says)...in that order.
(everybody) What's Your personal preference)?
Twin wheels from a mechanical point of view are more complicated than a single wheel. More cables, more drag, less sensitivity. What I want is twin rudders (on a large transom boat), not twin wheels. I want them by lots of reasons that have to do with efficiency and safety, but that is another story.
Regarding the wheel versus tiller. Tiller wins on simplicity, price and sensability. The wheel provides you with something you can hold on bad weather and gives you some support when the boat is going up and down on big waves. The choice, as Tdw as pointed out as to do also with the free space on the cockpit and with the rigging. A tiller permits you to reach farther, but takes away free space on the cockpit.
The reason that lead to twin wheels as to do with the transom increase in size. Modern boats have broader transom and beyond a certain width you can not sit on the side and reach the wheel, even if it is a big one (not to mention the ability to reach the winch with a hand on the wheel).
The size that justifies two wheels depends on the transom width, but it is around 40ft.
On boats with relatively narrow beams and transom (for modern design) you can still have one wheel (First 40, Elan 410) but on boats with large transom that would be impossible (Pogo 12.50, Opium 39).
Twin wheels have became a "fashion" and lots of boats that don't need twin wheels (smaller boats) now offer them as standard items (for comercial purposes). It is true that in what concerns access to the cockpit, a twin whell offers advantages, but that as nothing to do with efficiency and it is only understandable in an oriented cruising boat, not in a performance one.
Besides the efficiency problem you will have another problem with the localization of boat's instruments. Some brands just double everything, from the compass to the wind, speed and depth instruments. More expense and more complication.