Each manufacturer develops its own firmware to execute instructions. These differences are what give each vendor's products unique characteristics. Certain companies employ proprietary instruction sets, which are devoted to ensuring minimal latency. Other manufacturers focus on security and features like better error correction. While the purpose behind firmware is to instruct the hardware on how to perform its actions, it is as vital as the physical components on the board.
When I am looking for a new card, I often look to see which companies are providing updates to their firmware at a regular interval. This leads me to believe they are striving to maximize performance beyond what was first launched. Firmware releases are often found on the support pages of each NIC manufacturer’s website.
It is important to perform research on a specific manufacturer’s features to determine if they only work with other devices made by the same vendor. Since there is a standardization of data transmission, most efficiency increases fall outside of this standardization, making them proprietary. Therefore, spending extra money on a desired feature may be futile if purchased without the coupling router and matching network cards to other machines.