From what I've tried if you're talking about moist mash I'd stick with my flip top, the rectangles work better than the ovals at preventing the scratches. I don't have time for the whole soaking/fermentation thing but I believe it works.
They had a metal spinning kind at TSC that was intended...
The feeder itself makes a difference too. The common round one you screw on to a jar is easier for them to scratch the food out of. My current flock is about 4-5 weeks also and I noticed at about 3 weeks they started scratching it out worse. Raised does help but the flip top one they waste less...