[davyjones]

I developed and use(d) pgxplorer (github.com/pgxplorer). So, I can tell you this: the best out there is psql (CLI). There exists no use case where a GUI is better than psql.

[justinclift]

Not even diagramming relationships between tables?

[davyjones]

Those fall under db authoring/modeling tools. https://github.com/pgmodeler/pgmodeler is a good pick.