Wind Turbine Generator

I strongly suggest you refresh your knowledge of Maxwell's equations to try and understand your question and a possible answer to it. In particular you should reflect on Faraday's Law of Induction that describes the relationship between a changing magnetic field interacting with a conductor and the voltage produced in that conductor. Next you really should take a class on motor and generator design so that you'll understand the advantages and disadvantages of the many different types of generator topologies.

As for which type of rotor field production makes a more efficient generator, it depends on many more factors that you're not considering or specifying.

The most efficient generator can be a permanent magnet design used in an anemometer so that a precise wind velocity can be measured. However, by intended design this high efficiency design will not extract much energy from the air flow itself. At the same time a brushed rotor winding with some clever rotor current control circuitry can produce an anemometer with a wider range of accurate wind speed measurements.

In short, your two proffered configurations are not the only choices available for a generator. None of the actual choices are more efficient in an aspect than the others in every circumstance. Each configuration has advantages and disadvantages that make the energy conversion, assembly, control, implementation or availability more practical than another.

Neodymium magnets offer the strongest permanent magnetic field. However, for power production, the wound rotor with a regulated current through it's shunt field (Exciter generator) can control the alternator voltage very accurately. Most large power generators use exciters connected to the same shaft as the wound rotor. If your wind turbine is of the residential type a, like a vertical wind turbine, then the Neodymium magnets could be used to induce current (voltage) into a multiphase wound stator winding. In this case, the multi phase output would be rectified (diodes) to output a variable pulsating DC. The DC would then be filtered (to remove the pulsations by using super capacitor(s) to power a static inverter synchronized with (by) the utility frequency. Most of the manufacturers of vertical wind machines now use Neodymium magnets to levitate the weight of the generator on the tower shaft; thus boasting that the azimuth bearings are frictionless. A few even offer frictionless rotor bearings by magnetic levitation. Super capacitors are rated in Farads, where as common capacitors are rated in micro or pico farads. 500 farad (500 million micro farads) capacitors are available, but usually are rated at no more than 12 volts. They can be series connected to obtain higher operating voltages. Two 500 farad 12 volt capacitors connected in series would yield a 250 Farad 24 volt capacitor. Remember, however that AC and half wave DC voltages are RMS values. Capacitors will charge to peak, which is 1.41 times RMS.