Suited Vader relies on strength less? What the hell? He lifts a full-grown man two feet into the air, snaps his neck, and throws his corpse aside with one arm. That's inhuman strength right there. Watch also the Cloud City encounter. He beats Luke to the ground with his right arm, and towards the battle's end, hammers him like a madman. Vader relies on strength far more than his younger self, simply because he has it in incredible amounts.