The Pakari Nuva was the more powerful version of the Mask of Strength. It could increase the strength of its user and those around him to their ultimate.
The Pakari Nuva increased the raw strength of its user to amazing levels. The Great Mask of Strength. It increased the strength of the user and those around him to its ultimate.
The Kanohi Pakari Nuva was the Great Mask of Strength. It increased the strength of its user.
Krekka was probably a hair stronger than Onua Nuva when the latter had his Pakari Nuva.