Dear all,
I am trying to estimate a model for panel data and I was thinking about using System GMM. I have been reading Roodman (2009) and other papers, but I do not fully understand whether System GMM is able to control for unobserved heterogeneity or not. In other words, if I am sure I need to control for unit heterogeneity, would difference GMM be more robust than system GMM?

thank you in advance for your help

Best regards