most of the time (98%) i use fluxbox. it's fast, reliable, very easily configurable, reliable.... if i need some kde-application, i can load it in fluxbox without any problems
but to answer the poll i would say: kde. first because gnome reminds me of an operating system with a capital "X" in it's name (i love ambiguity
), second because most of the apps i use are kde-related... so i would say it's a question of habit, as the two (kde <--> gnome) are to almost 100% exchangeable...