The features that VLC can do, which SMPlayer cannot do, is that VLC can play the MIDI file with the SoundFont. This is something nice in Linux. Because playing MIDI file in Linux unlike Windows, need a SoundFont file and some configuration.
VLC is able to run the video capture device, such as webcam. This is what SMPlayer cannot do.
The next reason I use VLC is because, I don’t know what reason, sometimes SMPlayer pause the movie, then resume doesn’t work, but need to at least click the time navigator to resume.
For Windows, there is another superior application. So, I use VLC mainly for Linux.