Have you or would you go from Pentax to Sigma?

I have the Pentax 16-50mm and are considering the Sigma 17-50mm instead for enhanced sharpness. Of course the weather sealing and manual override on the Pentax are very nice to have. Now I have gained sharpness and better low light focus going from K-5 to K-5 IIs, so maybe the need for lens sharpness is less important.

Have any of you made the switch and what are your impressions, also when it comes to rendering, contrast and bokeh are these two lenses close to be in the same shrank? I guess for size they are about the same, except for the enormous lens hood on the Pentax.

Best regards

/Christian