Here's a trick question for you, which would you rather be hit by: An M-1(the rifle used in WWII, not the tank), or an M-16. Chances are, if you know nothing about rifles you'd have chosen the M-1, and you'd be incredibly sorry for it. Why? We've certainly seen the effectiveness of the M-16, in both war and peace. It certainly looks scarier. The M-1 looks at best like a hunting rifle in comparison, and really how dangerous could that be compared to an "assault" riffle?
First you need to know a few things about the M-1 Garrand. One of the most interesting features (for the purpose of the gun debate) is it is one of the only rifles that actually uses clips. There are no mechanical parts to the mechanism that holds the rounds you put into the rifle, whereas the updated version, the M-14 does actually use a magazine. The clip for a standard M-1, is only 8 rounds, whereas the M-16 is usually 20-30 rounds. The weight, 11 pounds vs 7 pounds (less if it's a carbine), would make you think the M-1 was more cumbersome. The fact that the M-1 was made before nifty things like laser pointers and forward vertical grips might lend one to think that the older "antiquated" rifle is less accurate, and thus not a "better" rifle. On all counts such assumptions would leave you dead (excuse the pun) wrong.
First let's look at the rounds. The M-1 uses the .308 or the .30-06. Both rounds are pretty large, and have significant muzzle velocity, and mass. Compared to the 5.56x45mm NATO standard round (.223) that the M-16 uses they are a little bit slower, but they also pack more of a punch. The sheer physics of the rounds would leave you to wish to be nowhere near the business end of the .308, but its what the rounds are actually designed to do where the real damage is.
You see the NATO standard round that we all know and love today was designed at a time we were really concerned with the horrors of war. The round was designed so that it would pierce light armor, but it was also designed with wounding, not killing a person in mind. To that end the rounds are small enough that the actual damage they cause is minimal (compared to the rounds previously used), and it was designed to keep on going after it had exited the body (think of it like the scene in Indiana Jones where he shoots three guys lined up behind each other). If you shoot someone with 5.56mm it'll enter and exit leaving behind small holes and not very large entrance/exit wounds.
The .308 by comparison is designed to stop inside a target, imparting as much energy as possible on the target. Most .308 rounds will actually mushroom, and deform. This has the effect of making the exit wounds significantly larger than the 5.56mm. As an added bonus the cavitation, that is the force of the wake of the round moving through its medium, is much stronger in the .308. The end result is that you can accomplish with one .308 round that it would take several 5.56mm rounds to accomplish.
Unfortunately in the gun debate, one side is basing most of their understanding of guns on bad hollywood movies, or worse talking points they don't even understand. If I were to give you the option to be shot by a bullet about the size of the tines on your fork, or a round the size of your pinky, which do you think you'd want to experience.