It's faster and smaller than the Splat Roller. It takes two hits by rolling (instead of one) to splat the opponent, so it's weaker, but at close enough range, pressing ZR to attack is still a one-hit KO. The attack is faster and has less range than the Splat Roller, though.

The sub weapon is the Burst Bomb and the special weapon is Inkzooka, which are both useful for beating opponents who are too far away for the weapon's tiny range.

Here's a video by GameXplain.