Deciding which network to use should be based on your unique home set-up.
The 2.4-GHz can be used for all your wireless devices. It can transmit data over longer distances and through walls and other solid objects. But, the 2.4-GHz band is more susceptible to interference, so speeds may not be as high.
The 5G-Hz band is ideal for newer devices such as your laptop, phone, or tablet because it can transmit higher amounts of data. However, it is less able to penetrate solid walls and objects, so if you are far away from your router, your signal strength may be lower.
Devices streaming a lot of video, such as Roku or Amazon Fire Stick, should connect to the 5G-Hz network, provided you can receive a strong wireless signal. If you cannot, use the 2.4-GHz.