So today i received my second 21.5 aoc monitor from staples, and i put them side to side to compare. One was connected using vga, and the other one was connected using dvi. What i noticed was that the dvi connected monitor produced a darker black than the vga one. Is this because of the connection type, or should i exchange it?

Swap and see!

I would chalk it up to the connection. While VGA can produce a picture on par with DVI it's by no means guaranteed to due to interference or other connection factors. Go with DVI and call it a day.

DVI quality much better than VGA

VGA will be blurrier, but you should be able to get the same black level via VGA as with DVI. Either the settings are different, the screens are different (despite being the "same"), etc.

Play with or reset the screen settings. Also, your graphics card could have differing per output settings. As suggested above, switch cables and see if the monitors change.

you can probably adjust both monitors to look the same

I have this on my work PC / dual monitors, one VGA one DVI.

The quality on the DVI is FAR better even though they are the exact same monitors and distance from the dock.

I have this on my work PC / dual monitors, one VGA one DVI.

The quality on the DVI is FAR better even though they are the exact same monitors and distance from the dock.
shouldn't be unless your port or cable is bad. True, DVI is better b/c of analog to digital conversion, but the converters are so good that there's really no signal loss.

When it comes to VGA, I've noticed, sometimes, that you can have interference with a poor cable that produces scrolling lines, among other signal artifacts. I had a crappy belkin cable that produced such interference that was cleared up when I used another, better VGA cable.

I also notice that sometimes VGA signals will produce variance in colors (almost like a very subtle film grain). However, the fidelity of VGA signals are very strong, so if you're noticing a difference in black levels between two monitors, it's more than likely a difference in monitors or a poor VGA cable.