It seems you have chosen three cameras that are in three different classes.
The DSLR, 7meg class, 8meg class
Here is a comparison of specifications:
The Pentax has fastest shutter.
All are good quality
None should be considered easy to use.
The most capable, most expensive is the Pentax.
You will need to know a good bit about photography (or willing to learn) to utilize it to the fullest.
I am looking for a new digital camera among Pentax *st Ds, Sony v-3, and Nikon 8800. Help me to choose one please. I only want fast speed shutter and good qulaity one and easy to use.