What are the advantages of a stock w/ a hook? Are the advantages primarily for bench rest shooting? Are there advantages when using a hooked stock off the bench?
Strikes me more as a preference. You can pull it into your arm a la M249 which I felt comfortable with. That, and if you use a fist under the stock you still have a place to hold onto.
Most benchrest shooters do not use stocks with hooks. They ride bags horrible, making free recoil very difficult to do. I like my hooked stocks better, because I have more control of the rifle with my support hand when manipulating a rear bag.