The main difference between $ and # is that:

$

$ is a compact way to access the Environment properties. But on the other hand you can’t execute a SpEL expression like you can do with #.

One example is


    @Value("${app.item.default.code}")
    private String defaultItemCode;

#

On the other hand # is used to evaluate expressions but you can also use it to pull information from the Environment altought it is not as compact as the $.

You can take as an example


@Value("#{environment['app.item.default.code']}")
private String defaultItemCode;

Conclusion

Use $ when you just need to access an Environment property and use # when you also need to execute a SpEL expression.