Did you know, that there are many variations of canned tuna? Me neither.
In Spain, most of the tuna sold in cans is either Atun or Bonito.
Atun is usually much cheaper than bonito, which is a kind of a luxury product. This mean that lot of the times it is packed in a more pretty tin can or a glass jar and served with better olive oil than the basic tin-can-atun.
As a fish, the more expensive bonito has a bit less fat/oil than atun, and the flakes seems a bit larger. The taste however is very similar in both fish, -in my opinion, atun is a bit tastier and has a slight metallic tang. The color of bonito has a yellowish hue and is lighter in color compared to the greyish atun.
Last time we checked in a supermarket, with the price of one can of bonito, you could get three cans of atun.