This is an interesting question. My thoughts are as follows:
'Illumine' is used in a literary metaphorical sense, more in the way of 'to enlighten', referring to the light of understanding.
'To illuminate' is better used in the material sense of a light source illuminating or lighting an environment.
However, 'illuminating' as an adjective is often used to describe a discussion that made a topic clearer and more readily understood. This type of intellectual comprehension is not the same as the spiritual or moral growth resulting from an enlightening realisation that has illumined the mind.
In writing, after clarifying the context, the word 'illumination' can be used to describe spiritual enlightenment, as distinct from the temporary, switch-on-switch-off event of mechanical illumination.