Having owned both, my vote goes to:
It has better longevity and projection (for me).
Your mileage may vary.
I like both fragrances but all things being equal, I always
place a premium on longevity and projection.
I wear fragrances, primarily, for my own enjoyment.
If I can't smell them, then I can't enjoy them, so the Boss gets
my vote over the YSL offering.
If you happen to like both, there's no reason why you couldn't own both.
They are different enough, IMO, to warrant having both in your wardrobe.