TN panels look great in games, their issue with appearance comes in the following:
1) Color shift (some people call this viewing angles, but this is not what the manufacturers call it) - Color shift will mean that at different angles, the colors appear slightly different. This is less relevant when it comes to games, as games uses textures and try to appear organic. Slight color shift really isn't noticeable in a game. This is more noticeable at the desktop.
2) Color accuracy. Good IPS panels have 8 bit colors, TN panels have 6 bit colors. That is to say, 8 bits per Red, green and blue, so it's more like 24 bit vs 18 bit color, depending on how you look at it. You'll be hard pressed to see the difference in a game, but if you look at gradients, which you may see in graphic art, you may notice a little less smoothness.
3) High resolution options - IPS panels come in 1440p and 1600p resolutions, TN panels top out at 1200p, but a 120hz version will be 1080p. Both require more power to be able to take advantage of it.
The downside of an IPS monitor, the ones with all the above advantages, is low response times, which results in ghosting, and a lack of 120hz for smoother and more responsive game play.
I suppose the choice might be similar to whether you prefer games which have very detailed textures, or one that has great animation. An IPS panel gives you a better still picture, a 120hz TN panel, gives you better animations.
QUESTION: Do you get headaches, nausea or eye strain when you play games in 1st person or over the shoulder views?
If so, a 120hz monitor with high FPS may relieve the symptoms of simulator sickness.
Are you a keyboard turner or mouse turner?
If so, you may not notice much issue with low latency and choppier game play.