Much much much less.
Not having to compile everything for days at a time, just to get 0.0005% speed increase, is a big benefit, in and of itself. Also, with Slackware, as long as you follow the directions during the install, then it will just simply and automagically work. Contrast this with Gentoo - I followed their install instructions _to the letter_, and the kernel wouldn't even be able to begin booting, while also screwing up my floppy drive in completely unwholesome ways. Definitely a very negative experience.