Why do you test wireless data rate and throughput with such applications and not with a local iPerf server?
Those speed test URLs depend on multiple things that you cannot control, like your WAN circuit QoS policy, WAN's oversubscription, the route of the traffic to the destination, the oversubscription in the WAN side of the remote server, and LAN side, the load of the server/s.
Add oversubscription on the RF medium to that, I mean, the number of concurrent users transmitting on the same channel that you are connected to, not to your AP, but to APs in the neighbourhood using that channel. Speed tests use to span over a time period that could make your wNIC to wait for the next transmission/reception, and that impacts the throughput. try to perform the same test over different hours as utilization may be differnt at the RF medium.
