I think it depend on the situation and company. In our company we like the 12rs 4 on 4 off pattern.
I must admit that we did try the 8hrs shift pattern, but we found it difficult for staff level, hoilday cover and some other issue arise from this.(I still enjoy to take 3 days hoilday for 12 days off)
During ealier hours in the morning is not always busy, but we got all the preparation work for the next day and some flight returning from the state.
BRGDS,
Sai