This isn't intended as edition war!
The thing that prompted me to do this was all the discussion about lethality, realism, etc. Not all of the criticism was based on comparisons to the previous edition, but some of it was and even when not, it's interesting to see how it differs in these aspects because it lets us consider what we were happy with about 1st, what we weren't and see how these things are different in 2nd.
I've done a combat with a party of four starting characters against a small group of attacking cultists and I've run it side by side under both rules systems. The characters are obviously slightly different but where I created a Feral World guardsman in one system, I created a Feral World guardsman in the other.
The results were interesting. I've written up the whole thing here and tried to make it engaging.
I may have made mistakes. I attempted not to.
Anyway, it took me a while and I'd be interested in what people think.