I'd always go for a high meat content wet food, its true you don't need to feed so much because it is more nutrient dense, so yes, cost would balance out, but if he likes the Whiskas and does ok on it I'd keep on with that and theres no reason why you couldnt introduce some of the higher meat content foods like Applaws every now and then. I don't feed dry as part of their meals - they have a few biscuits at bedtime (and as treats), but I'd go for good quality dry as others have suggested - the new Applaws dry, Hi-Life dry etc, but I wouldnt make dry the major part of diet as cats need the moisture from wet food.