I opened an original flavour Pixelmator file in Pixelmator Pro and noticed that the shadows applied by the Style looked quite faint. Upon investigation it turns out that I need to use exactly half the blur in Pixelmator Pro to achieve the effect I want.
I think that this is more of a bug than a matter of taste since a 4px blur in classic Pixelmator is visible exactly 4 pixels away from the object wheras a 4px blur in Pixelmator Pro is still visible 8px away from the object.
(Pixelmator Pro 1.0.8 on macOS 10.13.3)