[no subject]

As for throughput, you'll need hard numbers to make any judgments there.
   And it all depends on what you are doing too.  From what I've seen,
GTK is probably faster and light than Qt.  Signal propagation is known
to be faster, and in general, GTK is pretty quick, at least as fast as
Qt.  I highly doubt GTK takes up "much" memory compared to Qt either.

Frankly there are lots of reasons to choose one toolkit over the other
but simply "slow" or "much memory" are not initially valid reasons.
Rather ease of development, the richness of the widgets, the ability to
rapidly generate good, usable interfaces, and other factors are much,
much more important to you as a developer.  Whether or not and end user
thinks your program is slow often depends on how badly you've set up the
interface!