That is an incredibly vague question considering gun choice only has to do with (most importantly) what you think is cool and what has the features you'll use and so far we know neither about you. They all perform the same stock, but the AUG has a better gearbox than the MP5 which doesn't matter if you're not upgrading. After that, consider that MP5's have bad hi-caps and factor in any economical considerations (mp5s are cheaper, but not if you have to buy all std's). And then think about size and weight and feel and see if it is compatible with your play style. And bottom line, choose what is cool. That is really all the matters because even if you find a gun that has bad features, etc. you can always dish it off to someone who does like it, so just go ahead and feel one then decide which looks cooler.