I get what you are saying, but like police I don't particularly have a problem with the idea that prosecutors should be held to a higher standard. Using these cases as an example, I just don't get how it is ethical to basically provide two completely different accounts of the same murder in two different trials.
The burden of proof may lie with the prosecution, and yes putting together a case can be rough, I have several friends who are prosecutors, their workloads are often insane, however the State still wins about 90% of felony cases.
Public Defenders plead out about 90-95% of the time as well. The odds are still heavily stacked against the accused. The supposed difficulty in proving beyond a reasonable doubt doesn't seem to be borne out by reality.
Then you add things in like a confession being considered the gold standard of evidence, something that will change witness testimony and alibis and be more convincing than physical evidence. That gets problematic when 93% of people waive their Miranda Rights.
I'm not saying that prosecutors and cops don't have it rough, but defendants have it a hell of a lot rougher, especially poor ones.