What is the best type of diagram to show information flow through a system?

Many people use UML classes connected by dashed ‘information flow’ connectors. (“The IFD approach”). What are the benefits and also downsides, if any, of this approach?

I note already that an IFD like this is not defined in UML taxonomy, although widely used.

What other diagram types could be better to show information flow? Again… benefits and downsides?

Thanks