Are you including bottom bracket with crankset? I recently switched out a Tange cup-n-cone BB for a Chorus, at the same time switching from 105 crank to Mirage (so an upgrade on the BB, downgrade on cranks) and the difference was night and day in the Campagnolo's favour. It's a commonly overlooked component because hardly anybody ever actually sees it, but of all the moving parts it's under the most stress and, other than hubs, does the most moving.