Separate your Wi-Fi bands into separate SSID's for use on a single AP can add benefits you might not have thought of.
It might seem like the main advantage of using the same SSID is that your devices can roam between 2.4Ghz and 5Ghz and pick what they use. It is easy to set up on your devices and seems carefree.
The main disadvantage will come from the word “pick” in the previous description. What you should know is that most devices are not that good at picking a band. In many cases, they will fall back to signal strength to determine preference. As 2.4Ghz carries further than 5Ghz you will see your devices gradually all move to the 2.4Ghz band and the 5Ghz band is awkwardly empty. Why is this bad? Well, 2.4Ghz is extremely crowded hence despite signal strength being higher interference is quite an issue. On top of that 2.4Ghz is used for more legacy connections where 5Ghz will work and exploit newer technology. So while a typical 2.4Ghz connection will top out at 100Mb/s (at best!) a lot of 5Ghz connections can go much higher!
So why split? It allows you to pin your devices to 5Ghz where appropriate and switch back to 2.4Ghz if you notice that it does not work properly for some reason. A bit more cumbersome but in many cases, it will fix strange issues you may experience otherwise.
As a simple example. I have a desktop sitting about 15m from a dual-band router. If the SSID’s are the same it will initially connect to 5Ghz at a speed between 500Mb/s and 600Mb/s but within the hour it reverts back to 2.4Ghz. There it gets at best around 100Mb/s but very regularly it degrades to around 60Mb/s and due to interference there is quite a bit of loss. Splitting the SSID results in a perfect connection all the time on 5Ghz in the range of 500Mb/s to 600Mb/s.
So in summary making an SSID2.4Ghz and an SSID5Ghz is usually a good idea. You can even use the QoS settings to just favor your 5Ghz SSID and keep that for your own computers and laptops. Then broadcast the use of 2.4G SSID for guests, tablets, kids devices, and all other lower need devices. Set your QoS settings in the AP (Router) to throttle down 2.4GSSID when using the 5Ghz and you should never have a problem with bandwidth or band switching while using your 5Ghz Wi-Fi.