The size of the application is not the only non-functional criteria to take into account to choice between
J2EE "classical model" and Spring with Hibernate approach. You have to take into account the perenity, environment (knowledge of the team, current tools), support, ...
You have to manage the risk to adopt one approch or the other, and perhaps to realize a Proof of Concept (short duration project)
Unfortunately, the most influential criteria is 'political' like good relationship between an organization and product company, ...