Is the Nexus 4 still the Android performance king?

People are getting their hands on S4s and Ones and I'm seeing a lot of comments that the S4 is just as laggy as the recent pre-release videos and the One still isn't as smooth as the N4 through typical real world scenarios. Are we seeing the true extent these manufacturer's skins are having on smartphone performance? The One and S4 have a good 6 month's worth of spec advantage over the Nexus but this is seemingly obliterated by their heavy UIs (Touchwiz source being over 3x the size of stock Android)