Often, you’ll find that your router or access point will give you the option of two Wifi band. There is no better option but just what works best for your situation.
2.4ghz band travels at longer wavelength which will allow the band to travel further distance and penetrate through walls and floor but is prone to interferences. These interferences can cause your internet speed to decline.
5ghz band travels at a shorter wavelength and offer more channels which is less prone to interference but it unable to travel in distance. Due to the shorter wavelengths, 5ghz band is able to give a higher internet speed depending on how far you are away from your source.
Depending on what you are trying to accomplish, first ask yourself what you need the Wifi for and if speed and distance is a factor. This will help with where you want to place your router or access point in an area where speed is important but utilize the 2.4ghz band for distance.