Switching & Routing comparative analysis

I know this is a general question, but I'm looking for a technical comparison between different switches for enterprise use. I need make a competitive & technical compartive between Enterasys new PLATINUM cards, CISCO 6500 (OR SIMILAR) and Passport 8600 from NORTEL.I?m in the process of upgrading an network infrastructure and would like information on above switches. It?s very important the general issues and the possible throughput in a heavy Multicast network.
Any answer that increases my understanding will receive at least a share of the points.
Thanks!