BR's WAR is crap, well some people think all WAR is crap, but BR's is especially bad for hitting and pitching. I'm going to guess you mean fielding and pitching, but maybe there's something about hitting that I don't know about. As far as the pitching differences, they measure different things. bref uses ERA, so it measures the actual impact on the game, for the most part. Fangraphs uses FIP, which measures components, but not the runs that actually determine the outcome of the game. If you are trying to measure the value the pitcher had in the game, bref is going to be closer. If you want WAR to be something that you can use to predict future performance, fangraphs is going to do a better job.