none of these are very good. building on an Ubuntu base has always been a bad idea, be it for servers, desktops or whatever odd use-case you may have.

in the end, any of the Ubuntu flavors function really about as well as the others. see any Phoronix benchmark for proof of this.

if you want light, you follow the path of origination to the source. for graphical user environments this means something like Window Maker or TWM or Openbox. for distros this means Debian, Gentoo, Arch, etc. there are representative flavors available: Window Maker Live, CloverOS, and Crunchbang Plus Plus a few of my present darlings.

common wisdom buy-in has resulted in a state of mass hallucination that “light” is just a thinner coat of paint. get outside your comfort zone and you too can be astonished that light, taken seriously, can make your fifteen year old machine feel like the Chromebook if yesteryear.