I have ubuntu 12.04 (upgraded from 10.04) and since I disliked the default desktop, I installed lxde (sudo apt-get install lxde). This was good except that occasionally there would be trouble with Firefox (blinking on panel) so that finally I had to close it and then a error message from Ubuntu was issued. I had asked about it before but there was no useful response so now I want to move to another desktop which will hopefully not create the problem I have now. My doubt is, should I first uninstall lxde and then install kde (sudo apt-get install kde-standard) or is it enough to install kde without uninstalling lxde? In case it is necessary to uninstall, should I use the command sudo apt-get remove lxde or is there a better command for it?

You may also help me with choice of desktop. I installed lxde since this is simple and lightweight. I am assuming that kde will not be as simple but hopefully not create problem like above. But I hate if it takes too long to log in or to launch a program like Firefox etc and also there should not be icons fixed on the left part of terminal (I hate to keep icons on desktop since these are distracting). Some of these issues were present with default Ubuntu 12.04. So is my choice of kde-standard appropriate or are there better desktop alternatives?