Any reason to choose a Moroso vs. Canton oil accumulator? IIRC, Canton was the original and Moroso basically "borrowed" their design and marketed the same basic product. True?

Also, when one of these things is advertised as being 2 qt, 3 qt, etc., are they really adding 2 qt or 3 qt of oil to your oil system capacity? Or is some amount of that advertised volume going to be used for the air (chamber) that pressurizes the accumulator? If so, how much less of actual oil volume increase can be expected? Thanks!