I haven't noticed anything major as of yet, and anyway, you know how it goes: adoption usually speeds up bugfixes.
I'd recommend to start building with PySide2; by time your project is finished, it will be stable. Or else, worse case, you just change your import statements and leave the rest the same. ;)
I already have a large project that was ported from PySide1 to PyQt and it was non-trivial to do (sure most of it was the same but that couple of percent difference was a pain to find and update), so I'm not keen to repeat that experience until it's worth it. Sounds like maybe I should wait a bit longer or look into using qtpy as an abstraction layer.
I think that was a newer thing about Qt5...that PySide2 and PyQt5 had identical APIs. But I could be wrong. The abstraction layer sounds wise in any case.
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