Here is an useful test and quick review, which should answer the FAQs of quite some people who have been asking about the (performance) differences between the lenses. Btw, the Imatest results resemble many of my practical experiences and I in general do agree with the conclusions made by the author:-
http://erphotoreview.com/wordpress/?p=319&page=2
I do not do Imatest as an unqualified measurebator! ;-) But if you are still interested in my test for those Pentax standard zooms, here is mine - a real-life one! :=)
Read Also:-
Summary Matrix for Equipment Tests and Reviews