Aside from the head injury, my experience is that laser tag causes more injuries than paintball. For one, it's usually played in the dark amid all sorts of strange-shaped obstacles and artificially generated smoke. Plus there are usually little kids afoot that are easy to trip over.
I was with some buddies at Magic Mountain in Columbus, OH, when one of them wasn't looking where he was going, turned a corner and ran smack dab into an obstacle, breaking his nose and bleeding all over the place (he was a gamer, though; he kept playing until the music stopped and still managed to finish third in the group before we had to take him to the ER). I've also seen more twisted knees and rolled-up ankles from laser tag than I have from paintball (it doesn't help that many of the times I played laser tag in college, there was usually some drinking involved) where I think people tend to be a little more safety-conscious. Aside from the bruises, I think the average paintballer is less prone to injury than a laser tag player.