If you want to have a proper and uninterrupted gaming experience, you should undoubtedly use a 5 GHz frequency band.
You cannot use a 2.4 GHz frequency for playing games; therefore, for larger bandwidth and high graphics, 5 GHz frequency is much better.
In games that require good speed, you should use 5 GHz. If you notice that your games are lagging while playing, take it as a sign and switch to the 5 GHz frequency band.