I have one gravel bike set up tubeless, and one that is still tubed. I have never flatted (knock on wood) on the tubeless bike in the 2 years I've been riding it. It sees crappy, debris covered pavement, goat-head strewn fireroads, and rocky singletrack, with big rocks (funny, what we don't really have here is gravel:). I ride it in urban settings as well as everywhere I used to mountain bike.
I don't ride the tubed bike as much, maybe once a week (main reason being is that it's a singlespeed and it's all climbing here), but I will get a goathead puncture in that one, several times a year. Pretty tough tires too--Surly Knards--but still happens.
As always YMMV.