I think Operation Darkness came out so early that the PS3 wasn't a viable dev option yet. I remember reading an interview somewhere at some point lol. But you're right, it definitely would be a better fit on the PS3. Too bad it never got an enhanced port or something. I'm not familiar with Darkest Days though.
I'm super bummed—and ashamed!—that I didn't get in any good Halloween gaming (well, I did start Costume Quest). I've heard that the Tower mode in Darkstalkers is really hard too