I'd guess that they're not significantly better, nor are they likely to be any worse than a good balancing job, done by a trained, technician, on an accurate dynamic tire balancing machine. OTOH those are a few rather significant caveats.
They do add significantly to the unsprung weight of each wheel. To that end they probably detract slightly from the handling capabilities of the bike at the extreme. On a road bike it doesn't concern me.
Mostly, in my case, they allow me to mindlessly choose the least expensive shop to mount the tires that I buy on-line and to not bother with or worry about balancing the tires.
As far as noise goes; every now and then, at a very low speed I can hear a faint swishing noise. I don't find it objectionable. YMMV of course.