Up to you really. The size of the application doesn't particularaly matter - I'd personally use Hibernate for most DAO logic these days, unless the application was very basic, or a bulk loader.
Its not the volume of data that should be driving your decision, its portability and ease of use. If you go with
JDBC, you will have to write all the nuts and bolts to convert from entities to objects yourself. No biggy if there are not many entities. But if you ever have to change to a different database Hibernate is a godsend.
Whatever you choose, assuming you use a data access
pattern you should be able to swap your persistence technology easilly enough.