The newer material is slightly more stiff. After a bunch of wears though, it is pretty difficult to tell. The main difference is with lighting. The new material is more plastic, so it shines much brighter in the sun. Also, the newer material pops more when it's darker lighting. That's one reason why I prefer the mc3 over the mc1. The new material looks good in all lighting situations, whereas my mc1 looks brown/pea green in darker lit rooms.
The weave is also slightly different. You can really tell on the heel cup, as the pattern is different than the old models. I prefer the way the older weave looks, but it's not really a big deal.