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As with all things, it depends on what you want to do with the final images.

I always use png because it is a lossless format.

jpg makes smaller file sizes, but is lossy.  You wont see much difference on the image, but if you compile an image sequence into an animation using jpg, you are recompressing a lossy format, introducing more loss of quality.  png also shows some quality loss depending on what video format and codec you use.  In general, video is going to cause some quality  loss unless you go with uncompressed video, but that can run 4 GB for about 30 seconds.

So it's a huge compromise.

Ideally, just stick with png.  If file size becomes an issue for posting images online, then use jpg at various qualities until you hit the file size you want.

Sadly, there is no easy answer since things change depending upon what you want to do with the images.

Hope that helps!