What is the difference between the popular assemblies in Greece and Rome?

In Rome, the assembly of the people was called the Comitia. In Greece – Ecclesia. Roman meetings were divided into three types: in some of them only aristocrats took part, the second was held only for residents of certain areas, and in the third everyone could take part. Any citizen over the age of 20, but only a male, could take part in the Greek national assemblies. The Greek popular assemblies possessed practically unlimited power, while the decisions of the Roman assemblies could be vetoed – a ban on the adoption or implementation of any law.