Compared are the shortened UK DVD by Lionsgate (BBFC 12) and the uncut German DVD by Sony Pictures Home Entertainment (FSK 16).
There are 4 differences with a total length of 25.5 seconds:
3 cuts = 25.5 seconds
1 digital modification = no difference
To get the BBFC 12 rating, George Miller (Sin City) needed to make some modifications: three cuts were made plus one digital modification. This is also the version shown in movie theaters. The Uncut Version was released by Lionsgate on DVD and Blu-ray, is rated BBFC 15 and it's called "Extended Cut".
The two baddies threaten Ellen with their knives (two shots). Subsequently a shot of Ellen and the baddies looking up to Danny "The Spirit" Colt. With the shot of Danny, the UK Version is back in the game.
Danny hits Octopus in the water more often.
After Octopus' arm got torn up, one of his fingers flies straight to the camera. For the BBFC 12 rating, the finger has been removed digitally.
When Octopus explodes with the grenade, a piece of his ribs gets stuck in a wall.