So, if you're going to be soloing off the front in a road race, or bridging a gap, there's going to be a bit of advantage from facilitating a the IAB position.


If you're not going to ride IAB, the difference is vanishingly small.


If you're just riding around, the difference in speed from just the aerodynamics of the bars is not going to be perceptible.


If you're racing, the already extremely small aero difference is going to be minimized riding in a pack.


The fact that a number of pros choose not to use them indicates there no big advantage.


So, unless you ride IAB, I would get bars that you liked the feel, and look, of, and not worry about their aerodynamic properties.