Resizing the window looks pretty nasty on my machine (Windows 10, i7-4930K, 32GB, Radeon HD 7700) and I wanted to put a little screencast of me doing it to get a sense of how it compares to the performance on other people's machines. As you can see it's blacking out occassionally and is very choppy (this is a GIF at 30fps but even so, it doesn't look any better in "real life").
I have my size set to 100% all the time. I understand that dynamically resizing rescalable windows is more processor intensive than resizing normal windows, but you do expect far smoother performance than this on modern machines.
To add if I dynamically resize the window I would expect the value in preferences to change (as it will no longer be correctly indicated). Appreciate one is x+y and the other is a ratio but still that's what I would expect. Cheers.
Seems much better within Sonar esp when it's in the multidock.
Out of the multidock when resizing the UI often disappears showing a black screen instead (temporarily) for about half a second whilst resizing, just like the animated GIF in the first post, so I see no change in the OP's issue.