Differences- Marius is much wider. Shane is 3 stage and marius is a continuous rocker. I have heard that the marius isn't as fast as most continuous boards. Shane is fast for a 3 stage. Similarities- Both land soft. Marius is really popular because of it's soft landings and they maybe a lil softer than the shane.
I think the Shane is the better choice for you because it rides pretty loose but it holds well on edge and carries speed into the wake.