I have both the rolling boom and two sets of reef points in my main. I also have a bail for a vang and use it from time to time. Here are some observations I can share when comparing the two different reefing options.
Very true... and when running in heavy wind (good time to reef) a vang is very useful.
I know this is the prevailing wisdom and one of the reasons I have hanked headsails but..this has not been my observation with the rolling boom for the main. I find that I get a very nice sail shape, especially if I've taken care to roll the sail tightly around the boom. However I have found it very difficult and time consuming to reef the sail once underway. Single handed it is impossible. Short handed it is very hard. Usually you are reefing because the wind is up, and rolling the sail up on the boom with one hand, taming all of the lines with the other and steering the boat into the wind with our foot just doesn't work. It takes too long for one thing.
If I need to shorten sail once I'm already out, I use the slab system. However, If I see it is kind of rough before I head out, I will shorten sail using the rolling boom. It is VERY easy to let out sail using the rolling boom. So if the wind lightens or my nerve hardens during the day, I let out more sail simple by releasing the thumb screw and pulling on the halyard. Easypeasyleamonsqueezy.
Another thing about the rolling boom is that if you leave it free to roll with the sail all the way out, the foot takes on a nicer shape. You don't get that kringle in the foot that you normally see. Probably only adds 0.001kt to your boat speed but ...
That is definitely a plus... see photo.