Hi Ron.. I can tell you the 60 to 250 PENTAX lens is one fantastic versatile lens... it is as sharp as any lens out there. The only down part is its size and weight.. I have not used the 300, but considering the slight more focal length I would go for the 60/250 first.. but if you feel you are well covered already and your primary interest is telephoto..maybe birds etc.. then maybe the 300 would be worth considering. Obviously the 300 is far more specialized.
I have found the 60 to 250 to even be a great close focus/macro lens, even though it is not advertised as such.
I have the 17 to 70 Pentax and the 60 to 250 and this covers the most common needs.. I use them on a K5
I hope this helps..
Thank you for your response I am a serious Amateur who wants to start by investing in quality equipment Ron