This is, of course, an issue of personal belief in many ways. I would argue that the subculture and anomie theories work well together to describe why juveniles become delinquent.
Subculture theory holds that youths in some areas of cities create subcultures whose values are different from those of society at large. These cultures come to value things that the overall society sees as delinquent or deviant.
This is a very persuasive theory since youths growing up in impoverished areas generally have no role models other than those older people who are themselves delinquent. These people are often the ones who seem to be the most respected and the most materially wealthy. This would lead to a situation where youths look up to and emulate these people and the values they represent.
This theory can work well with the anomie theory. The anomie theory can help to explain why the people in these areas act in delinquent ways in the first place. In other words, anomie can help to explain why the delinquency starts, which then allows the delinquency to become part of the subculture.
Labelling seems much less persuasive because it implies that delinquency is only bad because society has labelled it that way. Many delinquent acts are inherently harmful both to those who commit them and their victims so I do not find this theory convincing.