Best landscape lens for K-5

Hi Pentax Forum,

I am a Sony Alpha shooter who is STRONGLY considering buying and switching over to a K-5. I have a read a ton of info from reviews, to ratings to forum posts. I am curious what current K-5 shooters feel is the best landscape lens for the K-5. It can be a prime or a zoom lens. I have been thinking about the 17-70 DA or 17-70 Sigma. Curious what current K-5 landscape shooters like the best as I can probably only afford one lens right now and I primarily shoot landscapes. Any input would be greatly appreciated since Pentax glass is all new to me. Thanks!