Well I just got done comparing 360 / PS3 versions, I made sure my TV was set identical between the two and both consoles are using HDMI, I adjusted the brightness on each version for best results using Bioshocks built in adjustment.
Unfortuantely my camera doesnt capture gamma / color correctly vs. what it looks like in person but you can still get an idea of the sharpness differances.
I was kinda surprised how much crisper 360's looks, especially when you first get out of the water and walk up the stairs, the bricks really look like they're wet on 360's while on PS3 it makes it look like my TV is a bit out of focus, anyhow here's what I got:
360:
PS3 (keep in mind I had the camera zoomed in on these shots)
TV is a 50" Pioneer Kuro Plasma.