Slitaz using Xorg, Openbox – GNU/Debian uses Xorg, LXDE/Openbox. So, PCManfm running desktop, LXpanel and Conky – identical setups with no services running.
Slitaz memory usage: 36.88 MB
Debian memory usage: 39.98 MB (post)
Well, it’s close. In fact it’s so close, I don’t know if it’s even enough to call a winner; ~3 MB is what it is, so my “clean system”, Debian setup uses roughly 8 % more memory compared to Slitaz.
If e.g. Firefox or Opera had a decrease of 8% memory usage, this would be significant.
Of course, this is very subjective – I may be wrong 😉