I'm looking at both of these lens and price wise their about the same.Reviews for the Sigma are very good where I've come across some reviews for the Pentax as so so.Does anybody own either of these lens and if so what do you think.I think I'm leaning towards the Sigma.It's a smaller zoom but I think the quality seems better.I mainly shoot landscapes so sharpness and resolution are paramount.
The Sigma is the better lens (among other things it's faster f1.8 vs f2.8) but it only has a 2x zoom.