Comment by cm3

xmonad has a built-in (xmonad-contrib) program launcher prompt that doesn't require an extra program and is more comfortable to use. There are other prompts included as well and you can build more prompts in Haskell. st used more memory and was slower than xterm last time I tried. I try using urxvt or st and only xterm works without problems or slowdowns. We may be using it in different ways and exercise different features of the terminal emulators :).