For dual band routers, the 5GHz band gives higher speed and 2.4GHz band gives more range but slower speeds.
In a real world experience, this factor only matters if you use an internet plan with more than 100Mbps speed.
For example, you can get 50Mbps full wifi speed on a 2.4GHz band only router. But 100Mbps will give maximum 70-80Mbps. To get full 100Mbps wifi speed, you will have to switch into a 5GHz band supported router.
This happens in below wifi 4 version /PHY 150..I had specifically subscribed 100 Mbps plan to understand and confirm Speeds..I got full speed in RN10 Pro which is wifi 4 version..U can check my speed test posts...Mine ONT is 2.4 MHz only..