Unless your travel patterns have you regularly purchasing int'l full fare tickets, then I would certainly not mess with the BXP2s. These Y & B fares can be 2-3x the price of the normal discounted coach rate, and of course there's no guarantee your upgrade(s) would clear.

From a pure bang for the buck perspective, 3,000 points will get you a roundtrip sAAver award in Y to Hawaii, easily worth $800-$1200 depending on when and where you're coming from.

From an ease of use perspective, the one segment NA upgrades (BXP1) at 650 points generally have lots of availability.