I just did quick measurements for vim 7.4 and emacs 23.4.1 in xterm, rxvt/urxvt, and gnome-terminal. The results depend most strongly on the terminal type. emacs' latency is always a bit (0.1-0.3ms or so) lower than vim's. Apart from that, xterm was around 1.1ms, (u)rxvt around 17.5ms, and gnome-terminal around 26.2ms. I wonder where the delay in rxvt compared to xterm comes from.
Depending how you're measuring it, I believe it could be because urxvt's output is buffered by default whereas xterm's isn't. That may mean 16.7ms (= 1 second / 60Hz) is added to the measured latency, though the extra time would have no effect in practice.
ed: or maybe thats excluded from the measurement but urxvt is double buffered by default?
You're right, urxvt refreshes at a maximum of 60Hz (line 1021 in http://cvs.schmorp.de/rxvt-unicode/src/command.C?view=markup). Above, I mistakenly measured only urxvt. Rxvt does a select() with a timeout of 5ms before redrawing (lines 1600 and 1664 in "src/command.c"). The total latency with rxvt is about 5.7ms.
