A3 and LR3 differ in a number of ways, the implementation of brushes being one of the more obvious.
Another that I have noticed is that in LR the contrast slider appears to respect the black point and exposure (white point) settings, whereas in A3 the contrast slider seems to push the data out beyond these requiring either a prediction in advance of where contrast will take pixels, or an iteration between C, B, and W sliders to arrive at the desired image.
Do others notice this difference? If so, how do you handle it, and which approach do you like better? Other thoughts on this topic?