They're completely different. PB is low budget, ambitious and tight, whereas CoR is lavish, lazy and crass. Money-wise, it's SW5 to SW4, plot-wise it's PotC sequels to PotC, style-wise it's... I don't know, something crap to something good.
The poster and everything I've seen for Chronicles, as someone else pointed out, makes it look like it's an entirely different franchise to Pitch Black - as in, the world it depicts.
Thought the casting in Chronicles was excellent, apart from Judi Dench. She just seems out of place, to me.
The story goes that Vin Diesel more or less pleaded with her to take on the role, plying her with shitloads of flowers and handwritten letters. He was a bit obsessed with getting her, to the extent where he more or less refused to film it if she didn't sign on.
I also prefer it to Pitch Black.
Do the two tie together at all well? I don't mean stories, I know the stories are different, but in terms of it gelling as the same character in the same world?
What kind of film is it compared to Pitch Black?