My very subjective test convinced me that I like the Dell better then BenQ. I have Dell 2407 at work. I ordered a BenQ FP241W for home.
I put both monitors on the same video card-6800 Ultra. Both were being driven by DVI. I used the Nvidia calibration wizard thing to calibrate both and at that point to me, the Dell was more sharp (not by much). The Dell blacks were blacker and the whites were whiter. This may not mean a hill of beans to anyone else.
I find myself always adjusting the BenQ to get the sweet spot, and adjusting the BenQ is a real pain in the but because you cant see the buttons. I have never once even thought about adjusting the Dell ( other than the above calibration). It looked perfect right out of the box AO3, I believe.
I will say the BenQ was brighter, too bright. I had to turn it down.
I pulled up Far Cry on both and saw no real difference, although, I did that test at two different times. I did the same with Two Towers. Again at two different times, but with Two Towers I was thinking I liked the Dell better.
I'm either RMA the BenQ or give it to the wife, she isn't nearly as picky as I am.
To summarize,
I tested them both side by side with a 6800 ultra and for code writing, surfing, office applications the Dell was the winner for me.
I tested them separately with Two Towers and FC and maybe saw a difference with Two Towers (Preferred Dell).
Hope this Helps.
BTW, If you go BenQ, Newegg has a promo on the BenQ right now. The coupon link is on the forum somewhere. Use that coupon and the price gets real close to the Dell.