If you feel confused or perplexed, I'm sorry for being unable to give you a definitive answer. Here's a website that I find invaluable: TFT Central
For example here's a review of the previously mentioned BenQ monitor.
Click on the Viewing Angles: Show the typical undesirable color shift of TN panel when viewed from the side. Lag: Skip the long text until the section "Lag Classification".
Yeah, I have been reading reviews from that website; the reviews are quite detail and comprehensive.
But for casual gamers of FPS, is it necessary? I mean do most gamers buy monitors with either of these technology? Or if the lag is in the class of gaming monitors, whether if it employs either of the technology does not matter?