Finger

From Openmoko

The sub-standard built in pointer that most humans have 8 of. Slightly less dextrous, though better positioned than the two thumbs and much better than the toes. Other appendages will not be supported.

The stylus has a more defined point, obscures less of the screen, and is less likely to leave greasy marks than the finger. The one benefit of the finger is that it is hard to lose, and not very likely to scratch the screen.