In real world, I do not see any difference in translating via Dynamic translation and a browser plugin. Both doing same stuff.

Regarding translation of email notification, I think it only translates fixed labels which we already do with standard translations by storing the content in Messages table.

For me, using Dynamic translation means;

1) Spending more moeny on Plugin for ServiceNow and also for translator service

2) Increases efforts and maintenance work for enabling translations for tables, fields etc. Not everything can be translated.

3) No option to switch if off or on for specific set of users. For instance, I want to enable it only for HR then I can't do that.

If I use browser plugins, all these things are possible.