The God of classical Calvinism and Arminianism is the same God, in the sense that their respective doctrines of God find resource in what Richard Muller identifies as ‘Christian Aristotelianism.’ How the Christian thinks of God will determine all else following, theologically. Since the actus purus (‘pure being’) god of Aristotle stands structurally and 
materially behind the way that Calvinism and Arminianism generally conceive of a God-world relation, what happens is that they must construct a system wherein this God remains untouched by said creation/world. In this effort, said systems have come to think of this God-world relation through a mechanism of decrees; what Barth, TFT et al. identify as the decretum absolutum (i.e., an Augustinian/Thomist inspired doctrine of predestination). Behind this conception of godness, i.e., the ‘unmoved mover,’ the ‘actual infinite,’ stands the notion that God is essentially monadic, singular, and impersonal. The only way this pure being god becomes “converted to Christianity” is by way of massaging said ‘godness categories’ into some form of commensurability with the triune God disclosed in Holy Scripture. This was Thomas Aquinas’ project, by and large; that is, to synthesize Aristotelian categories with Christian theology—which is why Richard Muller identifies the whole of the Post Reformation Reformed orthodox development, again, as Christian Aristotelianism (which is also inclusive of the Arminian way, as that follows Jacobus Arminius; himself, a bright scholastic Protestant thinker). In the end, what gets produced for the masses of Protestants who have come after such developments is to think God in a rather nomist (“law-ist”) way; as if God, in Himself, is first and foremost metaphysically defined by forensic categories. And so, we end up with things like Federal or Covenantal theology; or, the Canons of Dort (what has popularly been identified as the 5 Points of Calvinism; or, the Remonstrant or Arminian version of this with a soteriological focus on human agency vis-à-vis God [a system that rationalistically remains contingent upon the individual’s ‘free choice’ to be for God or against Him—and this choice, in juridical ways, can be reversed, based on the individual choosers of God]). At core, these systems, which unfortunately make up much of the conservative Protestant Christian ethos today, are grounded, as this sketch has been iterating, in a basic belief that God is first a singularity, and thus relates to the world in a detached impersonal way; that is, through decrees. Even if evangelicals are unaware of this background to the way they think God, salvation, so on and so forth, nevertheless, these remain the facts.
As is typical though in the usual binary thinking that funds the profane mind, in particular, when people start to get an inkling about this background to their respective theories of God and salvation, they will often swing the pendulum to an opposite extreme. They will go something like this: “okay, since I was taught to believe that God was really impersonal, related to me through law-like ways, even though glossed over by pietistic language, I will construct a notion of God by way of negation. I will construct a generous, winsome God who is simply the opposite of the law-ist (maybe legalistic) God I have been taught to believe in.” This is binary thinking: it’s a way of thought that is characterized by thinking in negative, even speculative terms. If one system of thought thinks God one way, and I hypothetically come to think God in an alternative way, the alternative way must entail negating this God. As a result, the binary thinker will negate the law-like features of God they have been taught, and assert, just as abstractly construed, a God who is defined by love (typically defined by socio-cultural mores rather than based on God’s Self-revelation). And so, when this happens, we end up with the classically liberal god, or the god of progressive and/or exvangelical atheology. In this frame, God is thought of, similarly, by way of appeal to speculation; it is just that an abstract notion of God’s law is displaced by an equally abstract notion of God’s love. Both approaches are fueled by appeal to profane thinking, whether that be supplied by classical Greek philosophers and/or 20th century existentialists and postmodern thinkers (to oversimplify).
There is a better way. And that is what I have been seeking to promote here at the blog (not to mention our books) for years now. It isn’t rooted in an abstract speculation about godness, and its ways. Instead, it is conditioned by being fully Christ concentrated; that is to say, by being fully triunely focused on the living God as Self-revealed and exegeted (see Jn 1.18) in Jesus Christ. This is not a tertium quid, but in fact an alternative, yet biblical way, to think God through the ‘logic of Grace’ (cf. TF Torrance) as, again, Self-revealed in the novum of His life for the world in Jesus Christ. To think God this way is to de jure rest upon the foundation which has been laid already in Christ alone for us. It is to think God from a concrete center in Himself for us, in Jesus Christ. It is to understand that our capacity to think God under these pressures is based purely in revealed categories and emphases, rather than in speculative constructs based upon the naked wits of a “natural humanity.” When we think God this way we think of Him, truly, as triune Love; as the One who by inner Self-definition, is engaged in a Self-givenness for the other in the inner-perichoretic frame of His divine and eternal life. And this then becomes the antecedent reality of a God-world relation. That is, God pre-destines Himself for us, as He freely elects Himself for us in the humanity of the eternal Son, to be God for, with, and in us forevermore. This type of predestination brings with it (Him) a new affectivity, a new rationality, a heavenly logic whose foundations are not of this world. This doctrine of God envelopes humanity in such a way that has always already been the free choice of God to be the Lamb of God slain before the foundations of the world. That is to say, this way of thinking God is based in a unilateralism of God, such that there is nothing Pelagianly present; there is nothing that we in an abstract or natural capacity have brought to God prior to encountering God in the concrete of His flowing and living blood for us in the veins of Immanuel. This is a different, not binary way to think God. We are ‘beggars all,’ as Luther rightly understood.
Hopefully, once again, this brief off the top sketch, will help to demonstrate just how different Evangelical Calvinism or Athanasian Reformed theology is juxtaposed with its competing, and underdeveloped counterparts (on the theological plane) as deposited in the annals of both classical Calvinist and Arminian theologies, respectively. I invite you to abandon these other ways, for the positive way (via positiva) I am seeking to promote here. amen amen