I think he is actually referring to ease of use and actual game play efficiency, not addon memory and all that garb
The reason I use uF addons is because I need them in the center of my screen or I will not pay attention to them. I also like the make the health and mana bar much bigger so they are easier to glance at. Coloring the frames by class is nice too because if I have an arena team of a druid and a rogue I can easily tell them apart without reading a name.
My favorite uF addon is ag_UF because it is amazingly easy to set up and does everything I want it to