Beyond the dimension of the batten -- there are a variety of structural differences between battens of the same general shape dealing with the balance between flexibility, resistance/allowance for bending, damping of fluttering, ability to take "compression" without buckling, etc., etc.
In your Hunter 240, assuming you have the conventional battens, I'd avoid getting too wild. Try calling North, Quantum, or any of the sail manufacturers and ask them what they use.