My expectation, when I tested these, was that one eraser would be a clear winner, and if I had to pick one, then I would choose the Staedtler Mars Plastic. But each of these erasers performed better with some pencils than others.
There’s one other aspect of erasers that I really like. Its the feel of it in my hand. One of the gentlemen on Erasable (I think it was Andy but I can’t remember at the moment) mentioned the Black Pearl as a “worry stone” — an object to hold in your hand while thinking and that is why I love the Black Pearl. I often find that I press it into the palm of my hand like a little river stone while I’m writing. Its strangely soothing.