Hi miniman82
Re your present quandary:
Quote: I tend to shoot more landscape than anything else.
Well, at the risk of stating the obvious, a Pentax 50 f/1.4 is going to give you a 35mm film equivalent coverage of 75mm, whilst the Sigma 17-70mm approximates to roughly 24 - 105mm. I imagine that 75mm would be pretty restrictive when attempting to capture panoramic landscapes, in which case I'd tend to opt for the Sigma. Hope this helps somewhat, but good luck which ever lens you eventually choose.
Best regards
Richard