They are equal in many ways. www.blurbusters.com has a pretty good review on both of them. The benefit to the XL2420TE though is that it comes with an nVidia 3D Vision transmitter built in, so you don't have to buy it separately like you would with the VG248QE if you ever want to try 3D Gaming.
That being said, I personally own a VG248QE and absolutely love it, and have no issues with visible scanlines or anything like that when using Lightboost in 120Hz or anything like that. They're identical in many ways, performance wise, the real benefit with the BenQ though is the built in transmitter.
[Quick Edit]
They have a review linked for the XL2420TE, that also then references the XL2420T. The XL2420TE is an upgraded version of the 2420T with better response time and no PWM in regular operation (non-Lightboost), which means anyone with eyes sensitive to the PWM effect will receive less eye strain. I don't have any issues personally with eyestrain on my VG248QE, but it's a feature worth noting.