For Database-First approach Entity Developer offers powerful naming rules, data type mapping customization, automatic detection of many-to-many associations, inheritances, etc.
For Model First, Entity Developer offers powerful mapping synchronization and allows you to preserve manual mapping changes when creating or updating the database.
Entity Developer provides many other features not available in Visual Studio Entity Data Model Designer. For example it supports model-database synchronization with possibility to select changes to apply. It supports all kinds of inheritance hierarchies, visual storage model editing, background model validation, etc.
oreover, new Entity Developer version offers the powerful model refactoring functionality that greatly simplifies and automates such operations as creating complex types from properties, common to several entities, or creating TPT or TPC hierarchies from several entities.
These features allows you to greatly increase your productivity when designing Entity Framework models with Entity Developer.