I'm no expert either, but I do have a certificate that says I am qualified to prepare and serve espresso 😛 Neither is really better as such. As others.have said, it is about consistency. Most people find it easier to adjust grind settings than tamp force and remain consistent. Why tamp at all? Tamping is there simply to compress the grounds into a solid mass so that when hit with pressurised water they don't move around. By the end of a shot the grounds have been compressed by 9 bar force for 30 sec. I tend to tamp quite hard, as I found out when on my barista training course. I find sticking to a heavy tamp gives me better consistency, but others find it easier to be consistent with gentle pressure. If faced with a full doser of ground coffee, I can modify my tamp to suit.