What is the difference between Data Rate and Throughput?

The data rate is the theoretical value that a system can achieve, so if there were no losses or interference the wireless link would provide a data rate of 250 Mbps. However in the real world, there will be interference and losses which will result in a lower bit rate. The throughput can be seen as a practical value that the wireless link can achieve.

So when you are building your system and making calculations, use the throughput value, as this is what the wireless link will provide when used in a real application.