The problem is, you set yourself up for a Supreme Court test with a lot of chips on the table , and if you lose -- you lose everything.
Once the Supreme Court clears its throat and says that gays have a God-given right to marry people of the same sex, your political landscape changes, and now you are the Blue Meanies trying to take something precious away from people who the Supreme Court says are in the right, rather than defending marriage against the pretensions of a bunch of upstart minoritarian morality-flouters. Your degree of difficulty in getting a constitutional amendment passed and ratified instantaneously goes off the scale.
With a statute, you are putting yourself in a situation in which you only get one chance to get it right, and the other side is actively trying to screw you in a (we are on notice) biased court.
I prefer the amendment route, because that drives a stake through the challengers' hearts for all time. Get the amendment ratified, and It's Over, your way. Back to the peace and quiet we enjoyed before this Goebbelsian assault on our self-respect, moral hygiene, and common sense.
Bookmarking an interesting discussion.