I've got the same monitor with a gf4 ti4200, and asked the same questions you did. I don't remember my research too much, but I eventually ended up going with the DVI cable. Like 345 said, the digital/analog/digital conversion will hurt performance.
On top of that, the 930B has a lot of calibration options that are taken care of automatically when the monitor is running on a pure digital connection.
Be careful buying that cable though; I went to Best Buy and Circuit City looking for one. Both stores tried to sell me a gold-plated DVI cable meant for home theater for around $100. They didn't even stock a standard one in the computer/monitor section. Eventually I went to Micro Center and found a regular 6 foot cable for 22 bucks.