Completely agree and was going to make this same point. The PIN system is a lot easier to "hack" considering that all numerical layouts are the same and all PIN's are four-digits. Thus you only have to see the area in which they are touching the screen to get something close if not exactly accurate to the correct PIN.

Same goes for the Android swipe pattern system except that if you turn off the pattern display it is much more difficult to detect since length and pattern can vary. However, on two separate occasions people have noted to me that they "now know my pattern" despite my being fairly fast and subtle with how I entered it.

All things considered, I think finger prints are much more secure for most people.