Zone def is weaker than m2m from my experience. oppfg% for my zone team is higher than the oppfg% for my m2m, even though I think my zone team has better players. 2-3 zone also suffers against 3pt shooting. You can go to 3-2 zone, but then you are giving up alot of inside positioning. This is a little problematic when a good team goes an inside out attack.
People have also said zone suffers a reb disadvantage, but I personally haven't seen much of that.
Advantage of zone is that you can run a short bench. This offers some strategic advantage in recruiting. You can take on a couple of stars and potentially battle for them and be willing to take on a mediocre backup or 2, with the goal of your studs going for 30 mpg.
Def matters in zone. Any given shot in near the perimeter, your guards have an equal opportunity to be the defender, so all around great defense is still good.