Defenses adjust to a player's strengths (at least in the playoffs) and a mid-range shot is an easier shot to take away if they decide to. Any positive is a positive, and being able to hit shots that defenses are being trained not to defend is more of a wrinkle than preferable or more fundamental. In other words, if he has a strong mid-range baseline shot, great, but it's better if he has that AND has developed more range. But, if I have to choose between 50% from 2 and easier to guard vs. 35+% from 3 and better spacing, it's not even a question that the latter is preferable.