This is a more basic design question with reference to the direction Hiberate is going.

Hibernate annotations define @Column with length and nullable
Hibernate validator defines @Length, @Max, @NotNull

According to the docs...
"Out of the box, Hibernate Annotations will translate the constraints you have defined for your entities into mapping metadata. For example, if a property of your entity is annotated @NotNull, its columns will be declared as not null in the DDL schema generated by Hibernate."

So, from the perspective of the schema, does it matter whether you use @Column.length or @Length to annotate your field? What if you declare both? (I do realize that @Length enables you to use the validator framework (in classes or view). Is one decision better than the other?

I think using the HV descriptor is a better decision. You will be able to validate at different levels, and hopefully that's the way the spec will go.

Technically speaking, the HV annotations will override the JPA annotations (for example if you have 2 different lengths).