I use that hub on a daily basis and honestly don't notice any drag even with the lights on. Mind you this is with 38mm tires which already have some rolling resistance on an upright hi-ten bicycle weighing 35lbs+, so your experience may vary.

It is my understanding that the generator part of the hub in both the Archer and Shimano Hubs are made by Sanyo, so the only real difference aside from the addition of a drum brake mechanism, may in fact be the quality of the bearings. Perhaps a mechanic has opened a hub to do a comparison at some point?