Finality:
I'd go for a KDS, it has no BNC connectors at the back but for about $600 for a 21" its a steal.
I don't know where you heard or saw that the KDS AV-21TF does _not_ have BNC connectors, because the one I have (and bought for friends) sure does. I'm using the BNC connectors right now.
Ajay:
And in terms of quality display, I also don't know what monitor technician you were speaking with. How much do you want to bet most of monitors these days (or at least some components within them) are made OUTSIDE of Japan? Did you know that Nikon, one of the leading camera manufacturers in the world, now makes their lenses in THAILAND? I would expect that Korea has a better QC system in place than Thailand. (No offense to the Thai, simply using it as a comparison)
I've used two 2040Us, three G500s, and three KDS AV-21TFs. I've used them rather extensively, tested them quite extensively, and have come to the conclusion that at the "bargain-bin" price of $700 the KDS holds its ground very well. Because it uses a Sony tube, I can't see a difference between it and the Sony G500, but I do believe that the engineering behind the tube was carefully thought out. I had so many problems with the Sony screen (the display would shake in the bottom left and upper right on all three units, and the screen would resize itself a few times when warming up - kind of gave the effect that it was bouncing off the edges) but there have been others who have had problems with the KDS AV-21TF. The Mitsubishi screen gave me problems as well - all two monitors had problems on the left hand side; an entire 1 inch strip (top to bottom) was very out of focus. I tried so many things to resolve it, but since I was unable to, those monitors went back to the retailer.
Therefore, to conclude that the KDS monitor is the worse thing in the monitor market and the Mitsubishi 2040U is the best is a show of ignorance, UNLESS you actually bought and tried those things out. As you can see, each monitor had its own weaknesses and strengths, but you can't make a judgement against the entire manufacturer or line unless you've actually tried them out.