For me the decision would come down to draw length. If you have a 29 inch draw length or longer then I think the FX would probably be the better choice as its longer axle to axle length would provide a better string angle. If your draw is under 29 inches then I think the Blackhawk would be the better choice as its higher IBO rating should help with the shorter than average powerstroke.

On the other hand I think you should consider the Stalker model from Bowtech' s lineup if you really want something to compare with the FX. The axle to axle length is about the same. The price is comparable and the brace height is slightly larger on the Stalker model.

Just something to think about.