I would use the Volvo pads and sacrifice a dirty wheel for safety and braking the way it was designed. Ever seen a Mercedes wheel? They get brake dust as much or more than Volvo. It's about doing the engineering right, not making the car self-cleaning.
Volvo pads are soft, as are the rotors. Both are meant to wear similarly and have matched braking friction. When you use an aftermarket pad that is harder, like PBR, you should also swap to another harder material disc like ATE powerslots because the heat generated on the stock rotors can make for warpped rotors or safety issues during emergency situations, changing the way the ABS responds to braking rates. Engineering the proper combination is not a simple task, so don't just throw the aftermarket pads on there without being prepared for the consequences of a failed braking system. Let Volvo do the engineering. Obviously they do pretty good job of it with some of the best brakes on any car out there.
--
'89 245 Sportwagon, '04 V70 2.5T Sportwagon