The 2.4 will give you better distance from the router/extender but it tends to have more chance of interference as more devices use those channels. The 5.0 is faster but less distance. A wired device is the best. If distance is not an issue then I would use the 5.0 as it is faster. The closer you are the better. Also on the RE450 which is an extender, you can set it up so the signal between the router and the extender is on on band such as 5.0 and the other band is is used between the extender and the devices. You may want to try that feature.