Its the long term health effects that must be considered. These only appear after many years of shift working and are the result of disturbed circadian rythms. Medical research tells us that shift workers have increased risks of high blood pressure, heart disease, stroke, digestive disorders and kidney failure. These are thought to be related to stress, induced by interruption of the normal circadian rythm.
12 hour work shifts cause the greatest disruption and the popular 4 on/4 off shift is based on the 12 hour shift. Lower risk is associated with 8 hour shifts - the three shift rotation that used to be popular in the heavy engineering production industries. Its the associated daily stand down of 16 hours that is the key to stress reduction. I don't see many of the 6 to 2/ 2 to 10/ 10 to 6 shifts being used in aviation these days, though.
By all means, vote for the 4 days on/4 days off if you like the 4 days off so much, but do remember that the ill health won't kick in until you are in your fifties. There's a price to pay for everything. In my own case the bypass surgery only cost me eight years shift pay in cash so I suppose I'm in profit, but I don't know the cash value of any years still to be knocked off my life.