i'm really not a fan of grillgrates
they're really only good for getting crisp clean marks
but even then, they mark too dark. the maillard reaction is where the marks come from. Sugars in food essentially caramelize into that nice golden brown mahogany.
With grill grates, this happens very fast because all of the heat is conducted directly to the surface of the grates.
Everything marked with grill grates will get a dark black mark, which is actually TOO dark. It's just like making caramel. You want your marks to be a rich brown/mahogany color. Black marks are burnt and bitter.
Plus they prevent fats and juices from dripping into the coals - which is where some of the best flavors come from!