I've got a couple of questions. 1) Who's Rich and where is his dome lighting? It has to be the greatest lighting of all time to be GI and cast hard edge shadows like that. 2) Are you really talking caustics or radostiy? The general look in all four renders looks the same to me (radosity), however, the caustics are different. but then again you are using two different programs that generate materials differently, and have different render engines.