The slot MAY help channel crap (gas? water, mud, slush, whatever)away.

I don't buy the part about the slave pistons acting differentially--not hydraulically possible, unless some pistons did not move (siezed like a plastic chrysler piston!).

And I don't think they tried to control squeal, unless to insure that ALL volvos have squeely brakes (so we know when we are stopping?)

There is probably a little more surface on a non-slotted pad.

if you saw it, wear a mask and keep it wet, regardless of pad composition.

I once heard that bonded pads were softer than riveted pads, if anyone cares...

I usually run the cheapest, although now I want a good set for my '84 242glt.