LaunchConfiguration Userdata vs AWS::CloudFormation::Init

In a cloudformation template, which are the differences between defining the initializazion script into the Userdata section of a LaunchConfiguration resource, or by using AWS::CloudFormation::Init metadata? In which cases should we prefer one over the other? Let's suppose I have to setup the EC2 instaces, based on this LaunchConfiguration, installing tomcat and defining some config file, and maybe copying some packages from an S3 bucket. It's better doing it via a Userdata bash script or via an AWS::CloudFormation::Init section?

Thanks.