I'm pretty sure that's false esa, do you have any proof??
Anyway, the difference is that with DVI, the signal is "pure." Meaning, it doesn't have to be converted. DVI uses a digital signal, and VGA uses analog. Monitors only use digital signals, so for VGA it has to be converted to a digital signal for it to be displayed. This conversion results in a loss of quality.
There's a decent difference in quality, I think everything looks a bit sharper with DVI.