The better Semi Metallic pads outperform conventional (low end) ceramics by a wide margin. In normal driving, a typical driver may not notice. (any of the better OEM's that choose ceramics, the swept area is increased by 25 to 33% when compared to the Semi Metallic) But when towing a 24 foot fishing boat, for example, ceramics "may" result in the inability to stop from speed, for a sudden red light and rolling into the intersection. The critical point is high temperature, high load friction.
In the end, I like Carbotech XP-8 pads better than anything else. Righteous stopping power, modest dust, low (but not no) noise. They are NOT rated, but the friction specs put them squarely at an HH rating.
After suffering 220K miles with various "name brand" ceramic pads in my Jag X-Type, I finally went to Wagner Semi Metallics with a GG rating, and quite simply, they are utterly fantastic for my spirited driving. Head and shoulders above the ceramic pads.
As always, quality pads have relatively accurate ratings.