I've used them for 6 years now for middle school choir ... they sound pretty decent ... however not professional voices so I couldn't compare with an adult choir.
They're good for the price, but making the jump to something like the Audio-Technica Pro 45 will make a world of difference. I have a handful of C-2s and NTG-1s, and I still use our one Pro 45 the most.
I haven't used the Pro 45s so I can't speak to those, but I've used a pair of C-2s on a church choir for a while now and am very happy with them for the price. I use them at a distance of around 5' for what it's worth.