The primary differences between the two frequencies are the range (coverage) and bandwidth (speed) that the bands provide. The 2.4GHz band provides coverage at a longer range but transmits data at slower speeds. The 5GHz band provides less coverage but transmits data at faster speeds.
The range is lower in the 5GHz band because higher frequencies cannot penetrate solid objects, such as walls and floors. However, higher frequencies allow data to be transmitted faster than lower frequencies, so the 5GHz band allows you to upload and download files faster.
Your WiFi connection on a particular frequency band can also be faster or slower because of interference from other devices. Many WiFi-enabled technologies and other household devices use the 2.4GHz band, including microwaves and garage door openers. When multiple devices attempt to use the same radio space, overcrowding occurs. The 5GHz band tends to have less overcrowding than the 2.4GHz band because fewer devices use it and because it has 23 channels for devices to use, while the 2.4GHz band has only 11 channels. If you’re experiencing a lot of interference from other devices, consider using the 5GHz band.
Connect all devices to 5GHz and then move devices over to 2.4GHz as needed. No network is the same, some devices may simply work better on 2.4. This can even change depending on the time of day due to how wireless frequency and interference works. Smart home devices that don't use a lot of data are best left on the 2.4GHz connection. Sometimes putting younger kids devices on 2.4GHz is smart as well because they usually don't need as much data. Occasionally, a weaker signal on 5G will still perform better than a stronger signal on 2.4. No network is the same, sometimes it is trial and error determining which network is best for which device.