Got a silver 'C', then after a three year lay off did my PPL - Solo'd after 3 hours.
Having flown with other PPL's who've done no gliding my main observation is they tend to be 'frightened' of the ground when it comes to landing.
having said that the Nav / RT / IF skills of the power person are more than most glider pilots have - but that's why the shorter conversion course emphasises these points.