Just a quick comparison, the s602z has more features, builds up very well on the shortcomings of the 6900z. Some forumners at dpreview, however, said that the pictures of s602z are worse than that of 6900z, presumably because of the smoothening effect of noise reduction. Don't know how true that is.
The 6900z is available between $1000-$1100 I think. I estimate the s602z to be around $1350-$1400.