Erasing is not just for removing mistakes. You can create texture with erasers, you can make white fur overlap dark fur, you can add highlights, and a number of other things. But like the blending tools, each eraser will give a different result. Here I used three vertical stripes. The far left is a 6B charcoal stick. The middle is also a 6B stipe, but then I smudged it with a chamois and pulled some of the charcoal to the right side. Then I tested four erasers.
On top is the quintessential kneaded eraser. I went over the area twice, first dabbing it, then dragging it (just below dab). Dabbing appears to pick up more of the material in the unblended charcoal. This is the eraser I use the most.
Next, I used my Clic eraser. This one is the best at erasing all the material and leaving the space as white as possible, which is why I use it for any total erasures (aka: mistakes).
The next eraser I hardly use, but only because I'm not comfortable with it yet. It is the Staedtler Mars plastic eraser that comes in a rectangle half wrapped in waxy paper. I think the biggest reason I don't like it is because it's so cumbersome - to get into small areas I'd have to cut a wedge off.
And finally is the Faber-Castell eraser pencil - literally a wood-cased pink eraser that you can sharpen to a point. I only use this for fine detail. The cons to this eraser are that it leaves pink eraser pieces on the paper which I have to pull off with the kneaded eraser, and that it is very hard to sharpen. I use a knife.
There are still other erasers out there that I don't have, like electric erasers and pink pearl erasers. They all leave different marks, or rather, remove marks differently.