I have tried both.
If you listen to the very first Yngwie stuff, from the Genesis album, it is the FS-1
I actually like both pickups alot. The BKP is a bit more "stratty" since it has more sparkle to it. Having said that I would only fit an FS-1 to a vintage instrument where it would be appropriate, or on a budget build. On a lovely new Fender I would go for the BKP.