How should data be selected from a table through joins?

By using SELECT to get the data of tabela_A by joining with tabela_B , normally, and assuming it to be the correct form, we use some of the JOIN commands. Ex:

SELECT codigo, nome FROM tabela_A a
INNER JOIN tabela_B b ON b.fk_tabela_B = a.codigo

However, the same condition I can get using the following syntax:

SELECT codigo, nome FROM tabela_A a, tabela_B
WHERE b.fk_tabela_B = a.codigo

The first example has an easier read, IMO, and the second example saves a few characters.

• But what's the difference in using the two?
• Are there performance issues or differential treatment of the data obtained?
• Can I say that only one of the examples is the correct way to do it?