The stock rom will probably be faster in synthetic benchmarks still since Qcom apparently sell improved versions of some code to paying OEMs. So I've heard at least. Not having to run the heavy skins probably still gives us an edge in normal use and perceived smoothness though.
This is what I've been told by others in the team at least.
+David van Tonder what is the difference in ROM size from the original TouchWiz? Assuming, stock takes up about 7 GB, I would venture to say CM is down around 2 or 3, this is going to free up a lot of precious storage space!
+David van Tonder i was wondering if the google edition S4 source code will help make builds more stable for the S4 US Carrier Variants ? Do you think as stable as the neexus 4? Or will only the google edition will be stable ?