I think S100 is a bit easier on and off, may have a more wet look (but not much is there is), attracts dust more than Natty's.
I actually prefer Natty's because it is a bit more durable, is more "clear", and definately attracts less dust. Natty's provides more reflection and basically emphasizes the underlying prepwork. So if you have a good base ie. polish and/or sealant, I feel Natty's is the way to go. S100 has more of it's own look.
I have both products, I like them both, I use them both, I don't think you could go wrong with either one of them.
Hope this helps.