What's the difference between "transmit rate" and "link speed"? On my MacBook Pro, System Information (or airport or option-clicking on the wifi status icon) reports a "transmit rate" of 176



while Networt Utility reports a "link speed" of 289



What's the difference between these two parameters?
You already see the answer in your screen shot.

The maximum possible rate is 289.

The current transmit rate is 176.