Some good points and interesting perspective there. Made me think.
I guess I am particularly curious about the Purpose (teleological) and Value (axiological) aspects involved when applying the "Experience Machine" to this question.
Note: let us stick to plain English rather than throwing around jargon though for now (much like with various nuances of Determinism).
Nozick tried to show that raw 'pleasures' are not necessarily what humans are pursuing. He pointed at the belief in the reality of the experience as being a factor that outweighs a pursuit of 'pleasure'.
Extracting this idea and applying to what is 'better' to believe, for the problem I have posed, shift the focus of the argumentation. By this I mean that we decide what is 'better' so how we Value the different positions matters.
Assuming Non-determinism (in any degree) can we provide evidence to state that belief in non-determinism trumps belief in determinism (as outlined in OP). I think we can.
The dynamic between living a so-called good life and living a life adhering to reality seem to be entwined. Reality seems to expose itself as the Purpose we carry for living; or rather, exposing reality is the Purpose for living.
Future is certainly tied up within this. Many people's access to 'pleasure' is generally in the immediate now, in temporal isolation, and in sensation. The Purpose is something more substantial as it is reality seeking.
The pleasure is ephemeral and perhaps an immediate reactionary guide; focus on the visceral experience. The Purpose both concrete and expansive in a temporal incompletion - we are always seeking reality through the real rather than abstractly measuring it in terms of 'pleasure'.
Note: I am trying to be concise here so as not to muddle the line of thinking.
Now, if we view Purpose as both reality led and reality leading - instead of goal driven - believing in no temporal Purpose (Determinism) clearly defeats Purpose as a led and leading aspect of human life. For non-determinism we then have the task of what that means as a Purpose led and leading being and to what extent our strain and stresses of responsibility factor in or not, then provide the evidence for this (if possible).
As an example of the ideas above (in case it is difficult to follow): I had a gut feeling that I should apply the thought experiment of the 'experience machine' to determinism vs non-determinism. The gut feeling is merely 'pleasure' directed, but the underlying mechanism of all this is Purpose. This reveals that a 'better' belief is the belief that drives Purpose, therefore believing in having purpose is certainly better than not believing in Purpose.
The only remaining question then is whether or not there is an optimal degree of belief in non-determinism and whether or not an argument for belief in determinism can be realised within these bounds?