As I see it, there is a big difference between the two. As Luther might have said: they are of a different spirit...

RE is subchristian (Van Til would say, antichristian) in the sense that it usually makes no distinction between the believer and the unbeliever in terms of their basic categories. E.g., they talk about "properly functioning" cognitive faculties, but regularly miss the fact that given the Fall, human cognitive faculties AS THEY ARE do not function properly as they ought. This is what Presuppositionalist apologetics (PA) calls the noetic effects of sin. RE proponents (such as Plantinga) love to talk about Calvin's "sensus divinitatis" (sense of deity), but miss the fact that Calvin uses the "sensus divinitatis" never to justify "properly functioning" faculties, but in order to explain why man is always inexcusable before the face of God.

RE would argue that belief in God may be "properly basic", given man as he "naturally" is.
PA says, belief in God is required (!), given man as he is "metaphysically": created in the image of God, full of revelation from within and without, always and everywhere accessible to God. Thus, in PA, God is not a man-made, rational axiom, but a fact of revelation. In RE, God is a belief one may have, is entitled to have, or may not have.
Thus, only PA can apply something like an "existential pressure" upon the unbeliefer to repent and believe, RE cannot do this at all.

"Properly basic belief" of RE is a question of "justification" - an epistemological category. Belief in God's existence (from the impossibility of the contrary) as in PA is not merely possible, but absolutely necessary - for everyone!
At the end of the day, I believe RE is (epistemological) self-defense, while PA is offensive apologetics!

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Sebastian Heck
PCA & yet to be founded Reformierte Kirche Deutschland
Ph.D. student at Theological Universiteit Apeldoorn/Netherlands
Church Planting in Germany
Reformation2Germany