Well i have not used SMPlayer but im an advanced VLC user and i will talk only about VLC. Here are my pros and cons.
- Not so good looking (skin is kind of awful and finding a good looking and functional is harder then it seems)
- Not meant to be music player (it can play music and playlists but its not good enough)
- Many options in order to customize everything.
+ Many options in order to customize everything.
+ Plays anything you throw at it without additional codec's packs
+ Plays incomplete and damaged files and reconstructs index (for example can be used in combination with qBitTorrent sequential download to play video while it downloads)
+ Track's syncing (starting from subtitles with video) is piece of cake, and there is option to search subtitles online, download them and load on current video file.
+ Many video output options, from aspect ratio and cropping to output device and technology used for rendering (like 2d, opengl or directx)
+ Recording output (audio and/or video) and taking snapshots (images).
+ Video capture
+ Converting (anything to anything)
+ Playing media files and streams from network
+ Broadcasting, video on demand and anything else you imagine...
There are many other things like effects, post processing (while playing), hardware acceleration and muc, much, more...But i wont use it as pros because they are way to advanced options for most people.