I routinely perform Scott-style preacher barbell curls with a wide grip and elbows close together, and have noticed increased development/detail in the inner-bicipital region with no change in BF levels; although lowering body fat will certainly help with visible definition for anyone.
If your goal is to achieve that biceps "split," then you may wish to devote attention to both heads of the bi's by incorporating close and wide grip curl work. Again, diet will help with visibility.
To add that extra dimension (roundness) to your anterior arm, consider performing exercises that emphasize the brachialis muscle, which runs almost parallel to, then eventually crosses under the the middle of the two bicep heads.
It is a popular belief that such movements may help add at least some "peak" to individuals who otherwise lack it. Spider-curls, concentration-curls, supine cable curls to the forehead, and other curl movements in which the elbows are away from your side accomplish this.
At the very least, you may add some overall size to the bi's, which no one ever complains about.