A little hard to tell from that picture. Let's first assume that both of these are actually rifles, and not just dummies, and that both are loaded with the rounds they are designed to shoot.
I'm assuming based on the question that one is a Mini-14 and one is an AR-15, but the bottom one could be one of several M-16 variants as well. Depending on what variant the black one is--whether it's an M16 or M16A1, A2, or a civilian AR-15 will determine whether it is capable of firing full auto (M16 or A1), 3-round burst (A2), or semi-auto (AR-15). I think it's fair to say that a fully-automatic firearm with otherwise the same ballistics as a semi-auto is "more dangerous" (same for a 3-round burst vs. semi-auto.) I believe the Mini-14 was only ever a civilian rifle, so it would necessarily be a semi-auto.
I'll assume that we're talking about a Mini-14 and an AR-15.
If I'm not mistaken, both fire the same round, the NATO 5.56x45 round, but it could be the .223 Remington--regardless, they are effectively the same. The ballistics of a single round fired will therefore be equal, or at least awfully close to equal. So, again, it's a wash. And both have essentially the same barrel, so effectively the same accuracy. We'll call that a wash. If I'm wrong, and one is more accurate than the other, then that one is marginally more dangerous (depending on how much more accurate it is).
As pictured, the Mini-14 appears to have a 20-round magazine. The AR-15 appears to be pictured with a 30-round magazine, so the person firing it has to reload approximately 50% less frequently if they are going on a shooting spree. That can be pretty significant in a fire fight. (Reloading is--apparently--often when mass-shooters are taken down; that's what happened in Tennessee at that school shooting this year, IIRC.) So I think it's fair to say it's "more dangerous," but only on the basis of the magazine shown. Also, I'm pretty confident you could put that same 30-round magazine in the Mini-14 without any trouble at all.
Additionally, the Mini-14 has iron sights, and a fixed stock. While I'm sure one can mount an optic site on a Mini-14, it isn't as easy as doing so on an AR-15 variant, which has a more functional modular rail system (not sure that's the right terminology, but that's the point). The AR-15 also has iron sights, but, again, it's easier to mount optics on it. The fixed stock makes it harder to modify the Mini-14 to put different grips or a bipod on it, which can improve its stability when firing, but I'm reasonably confident that you can purchase a bipod that will fit that rifle, and you could almost certainly take the rifle to a well-equipped shop that could fit it with a different grip system. Stability matters when shooting, so the ability to easily fit a bipod or different grip system also makes the AR-15 marginally more dangerous, but only in the sense that it is easier for a user to make it a more effective firearm than for the Mini-14--but a committed user of the Mini-14 will still be able to modify it in functionally equivalent ways.
As pictured, the AR-15 has a bayonet mount, I think. The Mini-14 pictured does not appear to, but I'm pretty sure some Mini-14s do have them, so we'll call that a wash, but if I'm wrong and the Mini-14 cannot mount a bayonet (or at least not without some kind of significant modification, that, again, makes the AR-15 marginally more dangerous).
Overall, I think it's fair to say that the AR-15 is marginally more dangerous than the Mini-14, particularly as pictured with different sized magazines. However, a person on the receiving end of a round fired by one versus the other won't care whether one has a bipod and the other one does not, or one has a larger magazine than the other. The ballistic effect of the round will be the same. And if they receive multiple wounds as a result of the same semi-auto rate of fire (which they both have)--again--they won't care about the marginal differences I've pointed out.
CD, Was that what you were looking for? :-)
