From what I remember, the default terminal emulator on OSX does not even allow customising the color palette! I was able to only change the foreground and background color, and forced to stick to one of the predefined themes for the rest. On the other hand, I doubt iterm2 can achieve the flexibility and customisability of urxvt, which for me is still the #1 terminal emulator. Just my two cents to add to the discussion :)