What is the best practice on using eval on values for integers, bools etc in xml record data files? I see it both used and not in the odoo source code

Example:

<record id="foo_bar" model="foo.bar">
    <field name="test">True</field>
    <field name="number">1</field>
</record>

vs

<record id="foo_bar" model="foo.bar">
    <field name="test" eval="True"/>
    <field name="number" eval="1"/>
</record>

Bonus question: If you don't use eval, does Odoo auto evaluate the value?