I don't think you can really compare the two products. OCSInventoryNG is mainly used for computer inventory, and it can also do software deployment. I think it also supports pretty well Windows systems.
Puppet/Chef/Salt/... are configuration management tools, they are more targeted to servers (even if they can also be used to workstations) and for *Nix systems. Windows is supported by Puppet (and others I think) but it's a 'second-class' support at the moment.
If you want to manage servers configuration, especially for *Nix ones, without doubt use a configuration management system like Puppet.
If you just want to inventory computers (Windows or Linux) you can choose OCSInventoryNG.
Other aspects needs to be evaluated like: software community size (with determines support facility, development speed...), facility to use it (configuration management are more complicated to get in but it's logical), etc, etc, etc.
