What is the difference between Brilliant II SYBR Green Master mix and Brilliant III, which one is better?

The difference between the two Master Mixes is that Brilliant II was optimized to work with earlier generation instruments such as the Agilent Mx3000P and Mx3005P. The Brilliant III Master Mix is a single-tube reagent designed for performing faster qPCR such as would be done on instruments such as the AriaMx. It utilizes shorter annealing/extension times that previous generation instruments could not use due to their slower ramp rates. The Master Mix includes two key components for optimal performance under fast cycling conditions

1.  A Mutated form of Taq DNA polymerase for faster replication
2. improved hot-start mechanism

The manuals for these kits may be downloaded at the following URLs:

Brilliant III Sybr MM : https://www.agilent.com/cs/library/usermanuals/public/600882.pdf

Brilliant II Sybr MM  : https://www.agilent.com/cs/library/usermanuals/public/600828.pdf