Here is how you can test which piece of code is faster:
% python -mtimeit "l=" 10000000 loops, best of 3: 0.0711 usec per loop % python -mtimeit "l=list()" 1000000 loops, best of 3: 0.297 usec per loop
However, in practice, this initialization is most likely an extremely small part of your program, so worrying about this is probably wrong-headed.
Readability is very subjective. I prefer , but some very knowledgable people, like Alex Martelli, prefer list() because it is pronounceable.