Considering we're talking about a whole array of applications, "it" is not very helpful. The LXDE environment should load quickly and be quite responsive, but OpenOffice and Iceweasel take a long time to start, and they're both a bit sluggish on the tablet. What part of KDE is more responsive? For me, the KDE environment is about the same as LXDE (although it takes a lot longer to start up), but the KOffice suite is definitely more responsive than OpenOffice and Konqueror is generally more responsive than Iceweasel. But many people prefer OpenOffice and Iceweasel and will live with some sluggishness.