[FFmpeg-user] What is the (technical) difference between -r and the fps filter?

[Werner Robitza]

>
> That is correct, please use -vf fps
> See also ticket #1578
>

Thanks Carl Eugen.

However the question still remains: what's the actual difference between
the filter and -r?
Is it generally not recommended to use the latter at all? Seems all over
the place in many examples…