They are both about the same levels in ZDDP, so that shouldn't be a deciding factor.
0W-30 has better cold pour characteristics and a bit more robust TBN (detergent) package.
5W-30 has lower NOACK volatility (less evaporation and burn off)
If he lives in a warm climate (Florida, Texas, etc..) and he intends on changing his oil at 15,000 miles or less, I would stick with the 5W-30.
If he lives in an extremely cold climate and drives his car year round, I would opt for the 0W-30.
I have the very next post in that thread. =)
I live in Minnesota and only drive it from april through october. I only put about 2,000 miles on the car last year, so only change the oil once a year. Should I stick with what I have?