I agree with jams0988 that it's two very different styles, but I don't think Mathias' changes can all be dismissed as a stylistic choice.
- The water looks more translucent and shiny, it catches the sunlight more.
- He's added more details to the ocean in the background, reflecting the sunlight
- He's added some light to the tree trunks on the left, which were extraordinarily dark before.
- He's given more depth to the clouds, the distant island, etc
- Bunch of other stuff
Of all these changes, I think Mathias' changes to the water were a particularly nice touch. It really added a new level of realism, IMO.
One thing that I don't like in either slym's latest version or Mathias' edit, is the position of the sun. The sun is touching the horizon, yet the amount of light used on various objects in the foreground and the choice of colours, doesn't really give the impression that the sun is almost gone. The colours are too vivid, too strong. If the sun wasn't there, I would have guessed that it was almost noon.
Maybe I'm wrong.