The best GUI library in python

[d2002xx]

I hope the GUI could work well when I compiling a program in
background (in my K6-2 400, running program other than compiler in
this kind of situation is allocated only about 10% to 15% CPU
resource)

Most programs such as opera and emacs works well, except for programs
using tk/tkinter.

Currently, I know only wxPython and PyQT, they are fast enough, but I
want to know are there any GUIs better than the two.