More of an opinion rather than official differences, but as others have said, that red/pink ahi tends to be fattier, and to me, has a heartier and yet more smooth/slick mouth feel. Albacore sashimi (which I can't stand seared and prefer it unadulteratedly raw sashimi) doesn't taste quite as "fishy" to me, and is often, as I like, served with ponzu... You rarely ever see ahi sashimi served with ponzu; in fact, I don't think I ever have, specifically on the menu, at least. Along the same lines of divergent serving styles, ahi is more often used in cut or hand rolls; albacore is used much less frequently in cut rolls.
Ahi and yellowfin are the same thing according to http://www.blueocean.org/seafood/ which is a good source for questions about fish from US waters including what's being overfished that you might not want to be a part of.
Ahi is just what yellowfin is called when it gets to some fishmarkets. Does that sound more exotic? Or more Japanese if you want it for sushi?
Albacore apparently doesn't hit retail markets but it might if a local fisherman caught it and sold it to a local market. Another reason to know your vendor and to know what you're buying.
Blue Ocean says most "chunk light" in cans is yellow fin or ahi.
No expert here but just a view from the outdoor grill.
Ahi/Yellowfin - Once they hit my fishmonger I'll buy either. Nice 3/4" to 1" steak 1-2 minutes per side on a hot grill. Seared outside, tender and bright red inside.
Albacore - NEVER hits my grill. They could not give me this for a dinner. As far as Jfood is concerned Albacore is Charlie Tuna and comes out of a can, goes with mayo on two slices of toasted bread.
I am sure others will kill my opinion of Albacore.
Someone else will provide more info I'm sure, but here's my take on it:
- Ahi is the traditional pinkish tuna - very nice raw but very different from my favorite, albacore or white tuna. The latter is a more delicate flavor to me, almost flinty like a white wine (that also happens to be flinty). When it's seared it has a really wonderful melt-in-the-mouth flavor.
Yellowfin is one type of ahi. (Though there's also yellowtail, which is supposedly a name for up to seven different kinds of fish, all or some of which may not be tuna.)
Here's the Wikipedia entry on tuna:
Albacore is a species of tuna. Ahi is a name for a couple species (here's a good link: http://www.wisegeek.com/what-is-ahi.htm).
Yellowtail is actually a Jack - similar/related to tuna, but not the same.
I'd say your description of ahi vs. albacore is pretty accurate. Ahi tends to be fattier/richer than albacore - or at least it should be.
I would add - be wary of ahi that is un-naturally pink or candy-apple red: usually marketed as "sushi grade", this tuna typically has been treated with CO2 to set its color by stopping the oxidation process... it still goes bad at the same rate it normally would but does not look it. Give this stuff a good smell before you buy it (if possible) or before you use it.
Natural #1 ahi (true sashimi grade) will typically be a deep red (blood red) in color when it is nice and fresh with an almost black blood line (if it has not been removed) and will turn brown as it ages (very noticeable on the blood line). It will also be pretty expensive.