I want correct reason which DAC is better Whether AD9777 or AD9125.
The AD9777 is the 16-bit member of a new pin-compatible family of high-speed dual Interpolating TxDAC+® converters with a maximum input data rate of 160...
AD9777 on Analog.com
This question doesn't have an straight answer unless you tell us about your application. It really depends on the application.
In general, AD9125 is a newer generation, faster speed, and more capable of direct synthesizing. Now it is your call to decide based on your application.