This question doesn't really make any sense. These aren't mutually exclusive options!

You can have an inline query inside a stored procedure:

create or replace procedure p is
  var int;
begin
  select col
  into   var 
  from (
    select 1 col from dual
  );
  
  dbms_output.put_line(var);
end p;
/
      
exec p;

PL/SQL procedure successfully completed.
1

In fact, it's a good idea to place all your queries in stored procedures. For more details on why, read Bryn Llewellyn's "Why PL/SQL?" whitepaper:

https://blogs.oracle.com/plsql-and-ebr/entry/why_use_pl_sql

But calling PL/SQL from SQL is generally not a great idea for a couple of reasons:

- It can slow your query down
- If the PL/SQL runs SQL, you can get unexpected/incorrect results!

The slowdown is due to context switches from SQL -> PL/SQL and back again:

http://www.oracle.com/technetwork/issue-archive/2015/15-jul/o45plsql-2543984.html

Though the 12c "pragma udf" does mitigate this:

https://mwidlake.wordpress.com/2015/11/04/pragma-udf-speeding-up-your-plsql-functions-called-from-sql/

To see why SQL calling PL/SQL calling SQL may give unexpected results, see:

https://blogs.oracle.com/sql/the-problem-with-sql-calling-plsql-calling-sql