Will using KDE programs use too much system resources?

[Dotan Cohen]

I have switched to Xfce from KDE because I find KDE to slow on my
machine (1.5gHz P4, 256MB RAM). Xfce is a little faster, or at least I
feel this way though I haven't timed with a stopwatch. At least there
is no lag between typing and seeing text on the screen on Xfce.

There are some KDE programs that I have come to rely upon, such as
Kopete and Kate. Will loading these programs use resources as if I was
on KDE? In other words, if I continue to use these programs, will I be
negating any benefit of Xfce over KDE?

Also, if I have KDE open in F7 and Xfce open in F8, will I loose out
on the speed benefits of Xfce by the fact that KDE is open in F7?

I have only a very limited knowledge of how windows managers work, so
if there is a technical reason for a given answer, I'd like to know it
so that I can learn. From what I could google, if there is a drawback
to using KDE apps in Xfce, it is because of libraries being loaded.
But is this persistant after I close the app? Thanks.

Dotan Cohen
http://EssentiaLinux.com