If you create those tables and add some test data and run both queries you will notice that you get the same exact plan. The two statements are identical.

As far as the locks go they will obtain the same locks you can't avoid locks being take on an update operation. It will have to request update locks are all rows that will be updated and then those locks will move to exclusive locks once they are all ready.

So it come down to readability and for that I prefer the first query using the "join" statement.