It is very important that the laser light is in a good visible color spectrum as well as the diodes have a very low divergence. The beam diametre at aperture is normally not relevant, especially over longer distances.
The laser beam should have a round beam shape in all colors, so all colors match 100% and give a perfect white.
The scan speed should fit the requirement (the more complex the application, the faster scanners are needed) and the laser output power should fit the application.
A professional laser display system should be computer controllable (and should be controlled by computer).