Q. Does DVI Make A Difference?
A. This can depend a lot of the monitor in question. DVI offers a pure digital end to end connection between the graphics card and the monitor. VGA on the other hand has to convert the signal to analogue. In theory, digital connections should therefore offer a superior picture quality and a sharper image. In practice, this can depend on the model in question. There are a number of sharpening algorithms utlised for modern VGA interfaces which vary in the quality of the analogue/digital conversion. Some modern screens have such good analogue connections that it is very hard, or even impossible, to tell the difference between VGA and DVI.
Typically screens which don't have DVI connections offer very good quality VGA connections. Perhaps manufacturers spent more time and effort perfecting these, knowing it was all they could offer the user. On the other hand, maybe manufacturers who offer both connections don't spend as much time or money making the VGA as good as it could be, since they assume users will always use DVI anyway. This seems logical, and i practice there is a host of screens which show this trend.
If you can use DVI, then you should, since it will offer the sharpest image available for the screen. If you are limited to VGA only, I'd suggest finding some user opinions or reviews about the PQ using this intercace.