I figured that the spoilers would work best on comparing the protagonists. I'll modify things a little.
Personally, I think A Machine For Pigs was much more successful at pulling off its ending twist. That, and unlike Bioshock which bogs itself down with tons of mindless and gratuitous violence designed to keep a violent gamer's mind from wandering, there's no disconnect between being horrified at the atrocities on-screen while you're simultaneously doing them.
I'm not at all saying that A Machine For Pigs ripped anything off of Bioshock, but only that they contain a lot of intriguing parallels. That being said, AMFP was much better value for its money than Bioshock Infinite - a tighter narrative with less padding - and I'd love to see what The Chinese Room could have done with even half the budget, manpower and time that Irrational Games had.
Also, inb4: