The AT&T product comes with a lot of correlation rules and orchestration rules. But when we install the system for a particular client, we have been looking at their business objectives and then trying to customize the system to meet their unique business requirements.  

For example, some of the clients would like to see what is happening on the perimeter and the traffic entering the network. This might be the case when they are concerned with any attacks always coming in a particular way or if there is any probing going on from outside parties. In other cases, the clients may be mostly trying to monitor what is going on inside their infrastructure and the focus is more internal to the network.  

AlienVault provides you these capabilities. AT&T Management Security Services provides you not only with these SIEM (Security Information and Event Management) part of security, but also other areas like behavioral analytics. They are all built into one single package. This is the advantage: you have everything in one package.