The Sigma 28/1.8 EX Macro focuses closer than the Pentax 31/1.8.
Seriously, I like the versatility a close focusing lens like this gives me. And its bokeh is not shabby at all.
If strong-armed, I might trade a 31mm Ltd for it
but it has a lot going for it as well.
P.S.: "Normal" is not what you want it to be. You can say a lens corresponds to how you look but that is not the definition of "normal" for a lens. Pentax is hopeless regarding its use of "normal". The Pentax FA 50/1.4 is described as being a normal lens. The times when this has been true have long gone for Pentax...