If by "more realistic colors" you mean more accurate colors, then the e-IPS panel would be better. This would primarily be due to wider viewing angles. However, both e-IPS and TN panels are 6-bit color monitors and they must use temporal dithering to create an approximate 16 million colors from the 256 thousand colors than 6-bit panels can actually create.
"more visible details in games" this is dependent on both static contrast ratio, viewing angles, and possible backlight bleeding issues. Both e-IPS and TN panels have similar static contrast ratio (basically 1000:1). Viewing angles on an e-IPS panel is better. Backlight bleeding is a "variable", based on my own experience, TN panel monitors tends to have more backlight bleeding issue from my experience. I must clarify that I am comparing TN panels I have used to S-PVA and H-IPS monitors that I have personally owned which ranged in price between $700 - $1,300.
There are other monitor specs that should also be considered....
As stated above, all current 120Hz monitors have TN panels. I have never used a 120Hz monitor, but gamers have stated that their gaming experience is a lot better due to potentially higher frame rates (based on the video card).
TN panels have faster response times, making them less likely to have ghosting effects.