Some people think that the heavier grinds help out a new shaver because, they are more forgiving to technique error...

Some think that heavier grinds shave heavier beards better..

Some think that the heavier ie: older blades have slightly softer steel, and therefore have a smoother edge....

There of course is no hard fast proof of any of this, as in much of this hobby, much is just opinion....

My advice is try as many different razors as you can after about 6 months of shaving, and then decide which work best for you....