The G2G mentioned by companies are totally fake nowadays. It will take you 10 minutes of research on the internet to find out that those "gaming" TN screens have the same total latency as the best IPS screens, if not even MORE.
Here is proof
http://www.tftcentral.co.uk/reviews/eizo_fg2421.htm , have a look at the Lag classification graph. You will see that the Eizo Foris "gaming" screen that goes up to 240Hz infact has 14-18ms total lag, while other IPS screens such as the Asus PB278Q has 15ms and some others are doing even better (because of bypassing certain circuits, mostly).
Personally I bought an IPS Iiyama xb2779qs and the reviews were saying it has around 20ms delay. But think about this: can you notice the difference between 80ms and 100ms in a game? Well I can't. Sure though ignoring all other factors we might easily get to very high real ms (connection, screen, mouse/keyboard, system etc).
That was for monitor lag. Now there is something else, its how much "clear" the image is in FAST movement (eg when you turn the camera quickly in the game). That is where 120Hz+ is useful and simply superior. But is it worth the total washed out colours or bad colour gradings (for those with FRC) of these cheap TN panels? That is something YOU have to decide. Personally I switched to high end IPS 2 years ago with the Asus PA246Q and now bought a new 27". I can tell you that I wouldn't mind the unnoticeable blurring of a high quality IPS, but I am sure than some models may be unbearable. On the other hand, there is just no way I would want to watch games and movies on a 20-year-old looking display. The fact is that on a good IPS, blurriness and bad responsiveness are NOT noticeable./existant. Comparing 10ms to 20ms is like comparing 50FPS to 60FPS.
In fact some IPS screens are using a pixel boosting method to increase the "smoothness" feeling of the 60Hz and it works really really well but it has 1 disadvantage: overshoot. I noticed this immediately on my Iiyama when I turn on this option, it is VERY obvious and annoying, so I keep it off.