Raw power is important, but is not the whole story. The laser's wavelength significantly affects how bright it appears.

This chart shows the eye's sensitivity to different wavelengths (colors). There are two curves, one for daytime vision and one for night vision.

As you can see, the maximum sensitivity for both curves is in the green wavelength. Blue and red light of the same power appear less than half as bright to the eye. An important factor when choosing a laser.