If my only use for the rifle was shooting at the range, I would get the one, I liked the best. Yes the 308 round costs more to shoot but how much are you planning on shooting? If a lot that is a factor, if only a few rounds now and then, I wouldn't worry about it. Also the intial cost of the rifle may be more depending upon which model AR you are considering. The cheapest I have seen the SOCOM II is about 1500 dollars where as a good AR can be had for less than 800 if you shop around but that is a one time cost anyway. As far as the AR jamming when dirty that is all relative, I have found the AR to be an extremely reliable rifle. Can you shoot it for ever and not clean it no, but can you put a couple of thousand rounds of quality ammo through it without it getting so dirty that it starts having stoppages yes. I don't know about the reliablity of the SOCOM II but I have put thousands of rounds through the M1A/M14 full size rifles and have no relability problems either so long as basic maintenance is preformed. But ulitmately, once again based on the intended use, I would buy which ever one had the highest fun factor for me. Either way you choose, I think you will enjoy shooting them a lot.