That presumes the "outer lats" can be worked more than the "inner lats." To me, that's getting into "upper/lower biceps" territory. As in, no such thing. Some guys may like the movement for simple variety, but I wouldn't make them the cornerstone of a back routine.
Use the grip width that allows an effective stretch and contraction for your frame (arm length, body type, etc). Going wider will reduce the ROM, as you said, which will tend to reduce the overall effectiveness of the pulldown. The wider out you grip, the more your arms are to the side rather than in front of the body, increasing the arm work while decreasing the back contribution.