Way beyond my scope of knowledge, so ill let someone else answer. I have been extremely happy with my cast iron 23 year old Craftsman.
Yesterday i spent some time building some sleds. Saturday i tried to make something that involved 45* angles and it turned out bad, so figured some sleds would solve that issue. went with a basic design using 3/4" birch plywood and solid oak for the runners.
http://i.imgur.com/fAvh4JT.jpg
http://i.imgur.com/ZSufwCb.jpg
While making the runners i figured it was a good time to make a zero clearance insert. On several occasions i have had little bits fall down into the opening creating a ruckus. Seen in the first pic above. Also made from oak