Possibly; because the application uses inheritance, this could force you to use LINQ to Entities. Also, you might want to use LINQ to Entities to communicate to the Oracle database, but you could still use traditional ADO.NET.

LINQ to Entities.

You can use LINQ to Entities for the SQL Server data access and for the Oracle data access. The number of tables should not affect your decision. LINQ to Entities also supports inheritance.

The Entity Framework enables you to generate the Entity Data Model from the existing database schema.

The Entity Framework enables you to represent an entity across multiple tables. For example, the Employee entity name data can be stored in one table, although other information, such as date of birth, might be in a different table. You’re not forced into a one entity per table mapping.

The Entity Framework supports inheritance mapping scenarios, such as table per type (TPT), that enable you to have a base table that maps to a base class and an additional table per type.