When i do pullups or chinups i allways do chest to bar, with a noticible pause at the top, maybe a second. I strive for quality over quantity, reps are not that important to me as currently i am only doing weighted pullups of 5 reps, or pullups on a Training board to strengthen my fingers (i rock climb), so again high reps is not used for finger safety. I have not tested for max reps in ages.
Reason for chest to bar?? Well when i squat i could stop at parallel, but i go ATG, same analogy here, i could stop at chins but i do chest.
End of the day whatever floats your boat

, But i guess if you were competing with a friend or whatever, then before hand 'rules' could be established:P
If your going through hell, keep going.