Here's a few threads on them. Personally, I went with the Terra Grapps because of the numbers of people who've been happy with them and I'm really glad that I did. They handle well for an A/T including in the sand so personally, I don't see any reason for the Dune Grapps unless you just want a cool looking mostly onroad tire because they do look really cool.
http://www.titantalk.com/forums/tita...ne#post1134138
http://www.titantalk.com/forums/tita...ne#post1184442
http://www.titantalk.com/forums/tita...ne#post1203933