Good Question. Not sure that I can answer it with any degree of certainty, this is my thoughts on it.
It is certain that for a given quantity of magnet you can get more out with teeth. It is also almost certainly going to be the fact that coils in slots will be better cooled than coils stuck onto a smooth core in an air gap. For a conventional machine running constantly at full load the slotted core seems to be universally accepted as the best compromise.
For wind power many factors change and the optimum requirements are different. Ignoring the issue of cogging ( which can be reduced to a level that doesn't affect the argument) iron loss is much more of a factor in a windmill alternator than an engine driven one. Conventional alternator design tells us that the best compromise is when the iron loss is equal to the copper loss, so conventional alternators are running with a high iron loss even though the best grade of iron is used consistent with cost.
For wind, high iron loss delays start up and restricts low wind performance so this means that you should work at flux densities in the iron well below that of a conventional alternator. In modern conventional alternators the flux is worked very high indeed and in most cases the teeth will be completely saturated. This keeps the total gap flux up as high as possible, keeping the turns down, reducing copper loss to a minimum and also keeping reactance effects and armature reaction low. This lets you get the highest possible output from the smallest machine.
With wind I suspect that the best compromise would be to not let the teeth get closer than mild saturation otherwise the core loss will start to eat into the low wind performance. For good start up I think that air gaps should be kept to 1mm or greater.
If with a reasonable gap you can push the total flux up even if the teeth are saturated then I am sure you will still increase output. If the teeth are short then the increase may still be quite a lot, if the teeth are long and the distance from the magnets to the unslotted core are greater than magnet length then I think the gain beyond saturation of the teeth will be small. Using punchings from low pole number motors gives you a very long tooth that is far from ideal for the many poles that are best suited to low speed PMA's.
Ultimately I think it depends on the type of slots, the number of poles, the possible effect of reactance and armature reaction and where you want to compromise the design.For maximum output and maximum efficiency in a gale then saturate the teeth. For a good all round machine with good start up and low wind performance then don't use small air gaps and don't saturate anything.
If you want the best possible results in low wind areas and are prepared to pay for longer magnets then I think the best design may not use teeth at all. Start up will then not be a limitation, iron loss will be the lowest possible and you will have no worry about armature reaction and you will not reach reactance limiting in the working range, it will behave like an air gap alternator.
I have to admit that slots do make the winding stronger, easier and better cooled and let you use cheaper magnets but I haven't built a machine with slots for 10 years and I suspect I shall never build another for the low wind areas around here.
Remember that when teeth are saturated you are looking at a slotless construction with an air gap equal roughly to the length of the teeth so ignoring iron loss you can think of the other factors having similar effect to an air gap machine, so long teeth equate to a very large air gap and low flux from short magnets.
Flux
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