The push flag decreases your throughput efficiency to reduce latency a little. It is used to signal that no more data is to follow so buffers can be flushed and data forwarded to the other end's app without waiting for more data. The use of the PSH flag is determined by the data communications protocol (not by device, OS, or end-user configuration)
See this article
The reasons why one PC is faster than another are legion. I expect you'd have to test carefully and provide more details to get useful help on this.