It depends on the situation.
But for a street friendly engine I think it better to build power with cylinder heads over cam.
There's a guy on here dyno his 340 and made 400 hp with stock 340 cam but used edlebrock heads.
To make 400hp with stock x heads you need to run around xe285h cam. Which would obviously be less streetable and harder on valvetrain. The stock cam is about par with comps xe250h so that's quite a few step ups in the cam department.