Quantum consciousness...

[The Grand Nudger]

I think that no.1 is one of those questions that seems informative..but..instead, sends us down the path of misconception and inevitable mistakes.  Perhaps it might be more informative to consider consciousness as one way among many to provide something that is advantageous, just as many mechanisms for flight and sight exist.  Experience of first person(a) and experience in first person(b) appear to confer at least some of the same advantages.  

If both phenomena rely, ultimately, on a shared fundamental mechanism..then it shouldn't come as a surprise to find that some examples of self aware organisms are members of subset a, and others subset b, or that members of subset a might at some point become members of subset b. 

If the question is framed more specifically, as in what does subset b confer over subset a, I don't know that a definitive answer can be given..or even that a definitive and uniform advantage exists.  A VOC scream is indicative of experience -of- first person...but...it's doubtful that it comes bundled with pain, and experience -in- first person.  We know how disadvantageous the experience of pain can be - it leads to poor decision making...and often enough the experience of pain comes at the precise moment when good decision making is crucial.  It would probably be nice to know when our bodies are severely damaged without having that input come bundled with something that has a tendency to make the situation that got us damaged even worse.  So points to the plant on that count.

OTOH, the experience of pain, experience -in- the first person, appears to build/support stronger social and sexual bonds.  For all their potential experience of self, voc signallers aren't forming families and throwing their lives down for each other on the small scale - or on a massive scale such as we see in tribal or industrial war. We find some reps capable of rudimentary kin selection, but that's as far as it goes. So points to us, there.  

In a field leveling assessment, both reps of both subsets are wildly successful.  Like all other living organisms, we're both the tip of the spear of our evolutionary development. Badass motherfuckers, descended from a long line of winners, from way back, lol. You'll find us both all over the globe living in largely the same environments..and not only that, in a symbiotic relationship with each other.  Many reps of subset a rely on us for their very existence, and we on them.  We've long leveraged them by exploiting their ability to protect themselves and their production of edible/useful tissue...whereas they leverage our very experience -in- first person..of how tasty x is and how pretty y is and how luxurious z in their cultivation and propagation. Who domesticated whom, in this relationship?

So, points to us both? It seems as though many species have hit on some subset of an ability that confers similar advantage even by disparate means.