As has been stated many times, WAR, like every other stat has its flaws, and no assessment should ever be made based on one stat alone. If you want the best assessment of a player, or the best comparison of two players, you look at as much information as you can.
That said, IF you were limited to using one stat only, WAR would be the best stat to use. It is the most comprehensive and it does give a very good idea of what a player's value to the the team was.