After upgrading from build 9879 to 9926 you will notice that there are two options during booting:
Windows Technical Preview i.e. Current as well as the Default OS
and Windows Rollback.
You can minimize this booting time to minimum.
In the Start Search write msconfig and press the Enter Key.
Click on Boot button you will get these two options. To minimize the booting delay I have put 3 seconds in Timeout box and clicked on OK or Apply.
You can also change the timer from the booting screen also.