What KCsingh is talking about is the overdrive mechanism. Basically, 144hz monitors push the limits, not just by having electronics that can handle 120hz or 144hz (often 144hz will stop video cards from downclocking, due to 144hz using a reduced "vertical total" --a VT lower than the default often stops cards from downclocking on the windows desktop), but very often by pushing the overdrive mechanism too excessively.
The lower the overdrive setting, the higher the response time, but the fewer response time acceleration artifacts you will get from pushing the overdrive circuit too hard.
The Benq Z series monitors were known for being the fastest monitors on the planet, but this came at the expense of some nice thick inverse ghosting, especially on white to dark (in motion) color transitions, with few options to reduce it at all (AMA premium gave you the advertised 1 ms response time (top of the screen) but the RTA artifacts were too intense to be usable by any sane person). AMA high was tuned for decent image quality in gaming while still giving low response time, but even THIS was a bit too liberal and there really SHOULD have been a Low setting. AMA off gave normal LCD response time with no RTA artifacts but you got the typical ghosting you get without an overdrive circuit.
The Benq XL2720Z included a new AMA setting that was secretly (and undocumented) put into version 4 firmware, which was basically the long asked for AMA low setting (which could be activated by turning on blur reduction and then going to AMA and setting it to high, overwriting the default AMA high calibration). This made things look far nicer (but since the AMA was reduced by 50% compared to AMA high, dropping the contrast to a very low value was required for best ghosting results or you got too much normal ghosting), but because this seemed to be some sort of test setting, any brightness, resolution or strobe changes would reset it instantly. This could have been a test setting for the later XL2730Z, as no one knows why this wasn't included in the 24" Z monitors that also came with a V4 firmware.
The Asus VG248QE had among the most balanced and pleasing overdrive settings of any other 24" monitor with the liberal Tracefree adjustments, and the ability to combine Lightboost mode with changing the overdrive gain through the service menu to affect lightboost, which could remove absolutely all AMA artifacts if you dropped the contrast while lowering the OD Gain (This was undocumented). Too bad the color depth and image quality took a huge nose dive if you did this. Was absolute golden for 2D side scrolling games in Lightboost mode, though.