DVI vs HDMI?

I can't see a difference in picture quality, and after some searching, I see they're basically the same, but I don't have many details. I'm wondering if and what would be the differences?
I run dual monitors and my normal setup is one DVI (25.5" monitor, which I run 1280x720) and one VGA (17" - 800x600)....Kinda outdated, I know, but it's what I'm used to. Everything's so tiny in 1920x1200...but is picture quality better? I guess I can't tell.
I just switched everything around and am running my 17" DVI in 800x600 and my 25.5 HDMI in 1920x1200. Can't tell any difference in either monitor. Watched a couple HD videos and played around with some websites, games, etc that I usually use.
Probably going back to what I'm used to..the blue and white...and my usual resolution.
Thanks for any help!

The only difference between DVI and HDMI is that HDMI carries audio, DVI does not. You will not notice a difference in picture quality.

However you should always keep the monitors at their native resolution (I'm guessing your 25.5in is 1920x1200). If the text is too small then just increase the font size in the Control Panel. Monitors generally look terrible at non-native resolutions.

It's not just the text, it's everything. I'm set up as I was before but I'll try increasing the size of everything in 1920x1200.

You'll get used to it eventually...