In Entity Framework, when you use the Key attribute on a property (or multiple properties for composite keys), Entity Framework will create primary keys for those properties in the database. By default, SQL Server will create a clustered index for the primary key. This is generally efficient for searching and sorting the data.
However, the selection between a clustered vs non-clustered index can have significant impacts, especially on large volumes of data.

Here's a brief description of both:

Clustered Index: The leaf nodes of a clustered index contain the data pages of the underlying table. The data rows are stored in order (based on the clustered index key) in these pages, which makes retrieval of data extremely fast when queried with the indexed column. But the drawback is that the insertion, deletion and sometimes update operations can become slower, because the database might need to rearrange the data pages to maintain the order.

Non-clustered Index: In a non-clustered index, the leaf nodes do not consist of data pages. Instead, they contain index rows and each index row contains a non-clustered key value and one or more row locators that point to the data record. Unlike a clustered indexed table, a non-clustered index table can have multiple non-clustered indexes, but too many can affect the performance of insert, update, and delete operations.

To answer the question, if your application does a lot of searches and sorts on the primary key fields, then the default clustered index could be beneficial. However, if your application does a lot of writes (inserts, updates, deletes), you may start facing performance issues as the database grows, because the database would need to maintain the order of the clustered index.

If your application is write-heavy, you could consider using IsClustered(false) to make a non-clustered index for your primary key. This typically increases performance for write operations.

However, all these depend on your specific use case, database structure, related tables, and query patterns. It's usually a good practice to profile your queries, monitor performance, and adjust your indexing strategy as necessary.

Please note the above considerations apply to SQL Server and may vary for other databases. Always test thoroughly with representative production data before making significant changes to your database schema or indexing strategy.