SQL Server JOINS vs Subquerys

Question

I was making some queries, and came the need to carry out the grouping of a table that was in a JOIN within the query. To illustrate.

Sales chart.

+----+---------+------------+----------+
| Id | Cliente |    Data    | Vendedor |
+----+---------+------------+----------+
|  1 |     123 | 2018-03-20 |       12 |
|  2 |     456 | 2018-03-20 |       34 |
+----+---------+------------+----------+

Key (Id)
Items of sales:

+-------+---------+------------+----------------+
| Venda | Produto | Quantidade | Valor_Unitario |
+-------+---------+------------+----------------+
|     1 |     123 |          3 |           5,50 |
|     1 |     456 |          9 |              5 |
|     2 |     789 |          5 |            7,0 |
|     2 |     101 |          7 |            7,0 |
+-------+---------+------------+----------------+

Key (Sale, Product)

The query I was writing was a simple JOIN.

SELECT * FROM vendas v INNER JOIN vendas_itens vi ON vi.Venda = v.Id

However, at one point, I wanted to know how much each sale is worth and the order information. Determined to possess such information, I wrote the two queries below.

SELECT V.*, 
SUM(Quantidade * Valor_Unitario) AS [Total]
FROM vendas v 
LEFT JOIN vendas_itens vi 
ON vi.Venda = v.Id 
GROUP BY V.Id, 
         V.Cliente, 
         V.Data, 
         V.Vendedor

And

SELECT V.*,
       (SELECT SUM(Quantidade * Valor_Unitario) 
        FROM vendas_itens vi 
        WHERE vi.Venda = v.Id ) AS [Total]
FROM vendas v 

I checked the implementation plan for both consultations, but there was only one difference.

I would like to know the following:

-What is the difference in performance between the two consultations? Is there an advantage between one and the other (apart from the fact that the second one writes less)? - (I’m still junior)Which one is more "professional"? Or was it just a matter of taste?

I did some tests on a table with 15k records and saw no difference in performance.

Any improvement on the question, just comment, please.

EDIT1: As well remembered by José, the first query should be LEFT, because the subquery will not limit the scope of the first table. And as he asked, there are no indexes in the tables, only the keys.

Answer 1

I would use the first one, I know it’s not a rule and it depends a lot on the amount of records in addition to other things, but in many cases using sub-queries makes the query a little less performative.