The second might make more power, if you can keep the loss from having to use slip rings down. One thing to consider, the larger sq ft' an S-rotor has, the more Torque your going to get. What a lot of people misunderstand is that an s-rotor is like a diesel, slow speed, lots of torque. A HAWT is like a gasoline engine, lower torque, but screeming speed.
A moderately sized s-rotor can not be stopped in a wind. You either keep it from starting or brake as much as you can (through the windings, mechanical device) I've torn impellers off trying to bring one to a stop, plus burned up the mechanical brake I had rigged.
Where most people go wrong (in my belief, I haven't proved it, and I'm one of those people) is that they follow Mike Hackleman and use a car alternator. This device is begging for a PMA, it needs super slow speeds, lots of power. I'm thinking a 6 or 7 ringed PMA.
Now, in your situation, 6 rows of magnets, 3 phase, that's 18 slip rings. I would think you lose more energy from those slip rings then by putting two units up with two PMA's. Unless you put the recitifier on the shaft, and I don't think that's a good idea (see the braking part...)
Also, they will have different speeds, no matter what. Different amounts of grease can make the speed vary. So it wouldn't be an exact calculation.
