In reply to Jelly Mould Surfer:
All of their shoes now appear to you the same rubber. 4.2mm TRAX rubber
http://www.evolvsports.com/about/trax-rubber/
I cant comment on the rubber as the only pair I have is an old comfy pair of Defy, Which came with EcoTrax. They have been resoled since.
Im guessing that you have given them a good spit clean, or even better taken a wire brush to them to remove the oxidized rubber.
The only people that could answer for sure about the rubber compounds would be Evolv.