When dragging a window to the right it snaps and takes up the right 50% of the screen.  Doing the same with another window to the left fills the rest of the 50% up.

While I agree 50 50 is an optimal default, I rarely continue with that % breakout.

I propose for an enhancement the opportunity to hover in the middle and drag to the right or the left, this will update in real time the two windows.
so you could end up with 80% 20% or 10% 90%.

Again, the current functionality is great, though it would be very convenient to beable to drag the area that both windows touch to resize both of them to the right and left.