I've heard and measured the BIC F12 - It's a great sub for $200 and won't try to play lower than what it can handle which is about 30hz. I've heard the Polk PSW505 but not measured it. It was coupled with some Def Tech mains with built in subwoofers. The deftech mains sounded bassier and cleaner without the Polk PSW505 than with it.
The F12 is generally considered the better sub from all the data I've seen on these two --- both are good values at the $200 pricepoint.
If I had to choose of the two - I'd pick the BIC F12 - - - especially after forum member gorilla83 who's owned both confirmed he liked the F12 better.