What a great invention for both coloured and graphite pencils!
A kneadable eraser grabs onto the pencil you have put onto your paper and removes the top layer. This eraser can be used to either lighten or completely erase an area. If however you want to erase an area completely clean, a kneadable eraser may not always clean it to the point you are wanting to achieve. If that is the case than I would probably use the kneadable eraser to remove the top layer and then a normal eraser to remove the rest of the pencil to reduce the likelihood of erasing hard enough to put a hole in the paper.
Note: This doesn’t mean you won’t put a hole in the paper, but it can reduce your liklihood of creating a hole by already removing some of the pencil so you don’t have to use as much effort with your normal eraser.
A kneadable eraser also has another great advantage beyond being able to lighten areas. For normal erasers, I find I try to use the edges to be able to erase small areas. A kneadable eraser is able to be pulled and molded into the shape you want to use to erase with. This is really helpful in an artwork when you want to lighten a certain shape or area. And as you get colour from the pencil you removed from your artwork onto your eraser, you can remold it to get a cleaner area to use.
There are also however downsides to using a kneadable eraser. As mentioned, they don’t always erase as cleanly as a normal eraser, so they may leave pencil behind. They can harden so it becomes harder to mold them. And if they fall on the floor they can pick up what they land on (like dirt from the floor).
If you are wanting to create artworks with pencil, I would definitely recommend using a kneadable eraser. Having used different brands, and as the general cost of kneadable erasers aren’t that expensive, I would suggest buying any brand and seeing how you find it.