Ridiculous question, you may say, of course it will be based on who reaches the 100-meter point first. There are other bottlenecks that can prevent this bandwidth from being fully utilized. Now consider what is measured in Layer 4 testing. All file transfers and web traffic use these protocols and thus application performance is determined by the bandwidth at this level. Even though the modem may be trained up at over 8 Mbps, if there are other bottlenecks, the end user will not see this level of throughput.
Many factors can lead to decreased throughput, such as excessive delay in the network.
One newly realized bottleneck with USB ADSL modems is the USB interface. Even though USB claims 12 Mbps throughput, this is simply not achievable. The actual throughput depends on the quality of the implementation. Throughput rates of USB ADSL modems have been measured from 2.5 Mbps to above 6 Mbps. While rates above 6 Mbps are sufficient for Full Rate ADSL traffic, rates in the 2-4 Mbps range are clearly too low.