Is there a reason to install, say, VLC from F-droid instead of play store?
Given the second para of your question, where you are sure of developer, I would go with downloading from Play Store -:


Faster updates. Updates from F-Droid are typically slower than Play Store, more noticeable if developer updates app very frequently. For instance, check out open source email app "FairEmail" and see the versions on Play Store and F-Droid. Admittedly, this is an extreme example because developer at times pushed out 3 updates per day!
If it is a paid app, it is easier to use Play Store while installing on a new device.
Not sure of this but I have noticed that non Play Store apps are at times not backed up by Google and restored on new devices. Backing up and restoring has too many factors, so wouldn't weigh this heavily.