Subquery v/s inner join in sql server

Usually joins will work faster than inner queries, but in reality it will depend on the execution plan generated by SQL Server. No matter how you write your query, SQL Server will always transform it on an execution plan. If it is "smart" enough to generate the same plan from both queries, you will get the same result.

Here and here some links to help.

In Sql Server Management Studio you can enable "Client Statistics" and also Include Actual Execution Plan. This will give you the ability to know precisely the execution time and load of each request.

Also between each request clean the cache to avoid cache side effect on performance

USE <YOURDATABASENAME>;
GO
CHECKPOINT;
GO
DBCC DROPCLEANBUFFERS;
GO

I think it's always best to see with our own eyes than relying on theory !