The PA28 and Cessna's are used by the biggest names in the training industry - Oxford, Flight Training Europe and Cabair. If they can manage to get people jobs in airlines like British Airways flying the A320 I think the PA28 and Cessna are perfectly good training tools - and therefore are well above the mark for the PPL. Go ahead and train with a glass cockpit, but don't moan when the GPS does not work and you have no idea where you are!