Hi Karl,
Let me try.
In physicalism (2a) the world is as it seems - solid, real and self-existent - and consciousness "emerges" from physicality at the information complexity of the human brain, so machines will soon become conscious and replace us. Yet today's computers are socially dumb [1], as their architecture doesn't support the self-awareness to conceive an "I" [2]. And piling up video boards in a supercomputer is like piling up rocks, you get a bigger heap but it is still a rock (machine). So physicalism is dominant but has its problems.
Enter solipsism (2b), where an observer "dreams" an unreal physical world. It argues that everything is mediated by my mind so is created by it, e.g. Harunyahya's "The secret beyond matter" http://www.youtube.com/watch?v=X04jN_xcLis If so, as you say, it will look real, as a dream does, at the time, but with no real external world out there, what makes it consistent? If no-one watches a forest, no tree can fall in it, but what if later one looks to find a tree fell - was a consistent past history also made up? Did we also fabricate the dinosaurs, or the billions of years of universe history? So that's a problem.
In extreme solipsism everything is created by my mind, so "you" don't exist, i.e. the theory doesn't generalize well! A weaker version is that consciousness creates the world by triggering wave function collapse, as in Schrödinger's cat and your star example. Yet if we are "observation central", how did the universe manage before we came along to collapse its spreading quantum waves by observing them? So that's another problem.
In contrast, in 2d, we are nothing special, as observer and observed are equal. The physical world arises from quantum interactions that are symmetric, i.e. if you "observe" a photon, it also "observes" you. If quantum collapse follows any quantum interaction, quantum uncertainty doesn't cumulate. It stops if the detector "sees" the photon, whether Schrödinger knows it or not. While in 2b, a conscious observer creates quantum collapse, in 2d the interaction of any "observers" does it. So that is one difference.
In a virtual reality, observations create the physical world, as quantum theory says, as if one looks left a left view is created and if one looks right another is shown. That observing a virtual reality creates (a view of) it cracks the quantum measurement problem. But in 2d, unlike 2b, there is still a real world "out there" (it just isn't the world we see), i.e. it generalizes ok. That is another difference.
Virtualism (2d) is the logical reverse of physicalism (2a). As physicalism postulates a physical substrate from whose interactions the conscious observer emerges, so virtualism postulates an observer substrate from whose interactions the physical world emerges. The "observer" in 2d is not us personally as human beings, but all existence "knowing" itself directly. So no tree falls in a forest unseen as the ground it hits "sees" it. There are no "gaps" here and no view history to recapitulate, as quantum reality has been simulating itself to itself from the beginning, i.e. the fundamental observer of the universe is not physical at all, let alone technical or biological, but the essence of consciousness in all things.
To sum up:
a. Physicalism was a good option before modern physics, but struggles to explain our consciousness.
b. Solipsism can explain consciousness but struggles with realism, and doesn't generalize well
c. Dualism is an illogical compromise to let us get on with business, as was the Copenhagen interpretation, i.e. a necessary "work-around".
d. Virtualism is an unexplored logical possibility that science can evaluate, that has implications for the data we get from world we observe.
Now, Conway shows logically that either the world, including us, is entirely mechanical, or if any part of it, like us, can be conscious (with free choice) then it must all be so [3]. In this view 2b and 2c attempt to "have ones cake and eat it too", leaving 2a and 2d as the only contenders.
But can physicalism account for quantum theory? Everett's many worlds theory, that every quantum choice spawns an alternate universe, is the "way-out" case for 2a. It invents a multiverse machine to contain the quantum ghost's randomness, postulating a "clockwork multiverse", where no choice is ever really made. Yet why should an immense multi-verse, like a doting parent with a video-camera, copy everything our universe might do?
The VR conjecture is the equally way-out case for 2d, that the quantum ghost is real and the physical world is its virtual shadow.
Whether the world we see is an objective reality, that exists in and of itself, or a virtual reality, that is created by processing, is a hypothesis about it that science should be able to evaluate by facts plus logic.
So now physics has two crazy, but consistent, explanations of the strange findings of modern physics to choose from. Lucky us.
kind regards. Brian Whitworth
References
[1] B. Whitworth and T. Liu, "Politeness as a Social Computing Requirement," in Handbook of Conversation Design for Instructional Applications, R. Luppicini, Ed. Hershey PA: IGI, 2008, pp. 419-436.
[2] B. Whitworth, "A Comparison of Human and Computer Information Processing," in Encyclopedia of Multimedia Technology and Networking, M. Pagani, Ed. Hershey PA: Information Science Reference, 2009, pp. 230-239, http://brianwhitworth.com/braincomputer.pdf
[3] J. Conway and S. Koch, "The free will theorem," Found. Phys., vol. 36, no. 10, pp. arXiv:quant-ph/0604079v1, 2006.