I don't think all this should be relevant - once it was launched at least one time, the OS should be able to tell that the binary hasn't changed, and thus signature verification is not necessary.

The comparison is using OS X 10.6 - I used to daily drive it and it was pretty snappy on my machine - which is corroborated by this guy's Twitter video capture.

As for Windows performance - Notepad/File Explorer might be slower than strictly necessary, but one of the advantages of Windows' backwards compatibility, is that I keep using the same stuff - Total Commander and Notepad++, that I used from the dawn of time, and those things haven't gotten slow (or haven't changed lol).