Nothing against slide sites etc, just something I started doing as I have a problem telling distances. As a deers chest is close to 16" in the area I hunt, I used two pins. At 20 yards, if I put the top pin on the deers back and the bottom pin is at the bottom of his chest the deer is approximetly 20 yards out. If the chest fits well within the two pins, the deer is over 25 yards out. Of course the size of the deer changes things, but it helps me guestimate distance. As the years have gone by, I'm much better at distances, I bought a range finder. I've still stuck with the two pins and kept my shots within 30 yards.
My recommendation for you is to find something your comfortable with and stick with it.