Both are excellent in low light. Better than the VX2000 and DSR-250. If you get the HPX-170, Barry Green’s book includes a CD with extra scene files. One of them is a low light scene file. The camera functions just fine in low light without the scene file.
I agree with Noah, if you can afford it, buy the HPX-170.
I own both the HPX-500 and HPX-170.
Steve Eisen
Eisen Video Productions
Board of Directors
Chicago Final Cut Pro Users Group