Hehe, just entered my zone.
Beef from Aberdeen-Angus cattle along with the Hereford was for long concidered the world's finest. (The world back then being such that the UK was boss). But the Hereford has a more yellowish fat, - or at least had in the older breeds.
Now, the Angus grows nicely fat and fatter meat means juicier.
Many other breeds of cattle are bread with them becoming larger (and perhaps also older) before the fattenings starts occuring and many of the bigger breeds are also fed as accurately as possible for "red" meat.
(Intensive feeding, balancing protein and energy as accurately as possible for this, as well as the bulls not being castrated, then limited movement etc.)
So, today in short, true Angus beef is from an animal that gets fatter sooner, and is fed differently, and the final word of Aberdeen-Angus bloodline.
However, if you're buying Angus beef, I have no idea if it's a marketing ploy or if it is the real stuff.
The PETA person I know was an au-pair on my home. She ate the Angus beef with ease and delight.