Great topic as I'm in the same position of being a PPL student just about to buy a headset.
I have tried Peltor which are very comfortable and seem to offer good sound quality and have a Pilot PA17-79 DNC on long tern loan from a pal.
I reckon the Peltor are excellent value but the sound cancelling from the Pilot makes them very good to use in noisier cockpits.
All our instructors use standard headsets,David Clarke,Sennheiser and Peltor.
Are David Clarke sets more expensive as we are paying for the name?
Lister