No, TN doesn't have a 1ms response time, it is closer to 3ms. No, IPS/PLS/AHVA doesn't have a 4ms response time, its closer to 6ms.

Should 1ms vs 4ms (or even 3ms vs 6ms) be the deciding factor for you in your monitor / "gaming monitor" purchase? Absolutely not!! What matters is not just grey to grey transitions. You have to add in input lag and calculate the "Total Display Lag", which TFT Central defines as 1/2 the average response time plus the input lag. This is how long a change will take to register on the screen that the user can react to.

So let's look at some numbers! A common TN Monitor is the Dell S2716DG, and a common IPS/AHVA Monitor is the Predator XB270HU/XB271HU (same panel in the 70 and 71, one has a bezel and the other is bezel-less). The source for the below data is TFTCentral.

Dell S2716DG

Average Response Time: 3.1ms

Average RTC Overshoot: 4.0%

Input Lag: 2.7ms

Total Display Lag: 4.25ms

Acer Predator XB270HU/XB271HU

Average Response Time: 5.5 ms

Average RTS Overshoot: 0.3%

Input Lag: 0.25 ms

Total Display Lag: 3.00ms

The AHVA/IPS display is actually better than the TN display in Total Display Lag, and much better in RTC overshoot (reverse ghosting).

But that above statement is a bit disingenuous because there's more to this than just raw numbers. Humans cannot tell the difference between 4.25ms and 3.00ms and don't react fast enough to make the difference matter. Here, go measure you reaction time. It's likely to be in the 200-350ms range, which is 200+ times the difference between the total display lag of these two popular monitors.

1ms is a myth. 4ms is a myth. What actually matters is total display lag, which can vary wildly between panels. A TN monitor can be much, much worse than an IPS, PLS, AHVA, or even VA monitor. Also... you are not a professional gamer with super human reaction time. The difference in total display lag being 1.25ms (in the example above) is not going to help you when it takes you 200-300ms to react to the change you saw on the screen.

But... let's say you have super human reaction time, and you can react to the test above in just 75ms. The difference between the two monitors is then that you react in 79.25ms total if using the TN display, and 78.00ms if you were using the AHVA display. A difference of only 1.58%. Your reaction time has a variance higher than 1.58%, so this is within margin or error!

Since you aren't super human, you are more likely in the 250-350 range, making the difference just 0.49% (250ms reaction time) or 0.35% (350ms reaction time). So... the difference is actually basically zero.

The Bottom Line: Do your research before you buy a monitor, and buy the best monitor you can. So many people skimp out on their monitor despite it being the way that they interact with their machine when they use it. You stare at the monitor every time you use the machine. The monitor is the gateway to the machine. Spend the money to get a nice one. That 1300 dollar video card is great and all, but when you connect it to your 120 dollar "gaming" TN display with 10+ ms of total input lag, shitty colors, shitty gamma, shitty viewing angles... your whole experience is shitty.