For a 50 cal, I'd get 3F and if you can't get it out of your mind, get a can of 4F. It'll last a very very long time even if you prime every shot with it. 2F is perfectly serviceable in a 50, so If you'd like to work up a load with 3F and 2F to see which your gun actually prefers, then get a # of 2F.
Just know that you'll need to develop a different load for it for best performance (and for me, accuracy _is_ performance). No amount of "energy" counts if you miss the intended target.
Once you get your loads worked up, you'll know if 3F or 2F works best in your 50 cal. Only you can do that. Everyone can tell you what -his- gun prefers (if he's worked with two powders, some haven') but no one can tell you what your gun prefers, as you load it. Enjoy the process. Do your accuracy testing at 50. 25 yards makes everything look wonderful.
