Neither - whilst the canon 100mm IS L does add some good new features (like internal focusing, image stabalization and teleconverter compatability) its image quality is not really that different from the original 100mm macro. Any differences present will only really show up in a controled studio test shot and then factors such as manufacture tollerances will lead to more differences.
In addition outside of the studio test setup = real world shooting = you won't notice much if any image quality difference as a result of the glass alone - however shooting methods, lighting and such will have a far more dramatic effect.