The reason cloverfield got a 15 is because the level of psychological threat and intensity was higher, so the bbfc gave the film a 15, terminator 3 used alot of fantasy violence such as when the two terminators were fighting, so the context it was based in is mostly fantasy e.g. judgement day, and also a shape shifting antagonist. The strong language was infrequent, and each time was aimed at the terminator, and was non sexual in context , which the bbfc allow, and the part when the tx puts her hand through the police officers stomach is strong but fantastical in context too. The unrated version of terminator salvation too is only a 12 in the u.k and so is the uncut version of fast five. It dosent take genius to work the above out.