" If it's worth saying, spell it out. And if it's not, then don't clutter the webpage as long as the products are the same with the exception of fill power."
Except that for some customers, they're not the same even though the performance is the same. We've been super happy with the duck down, and don't see any performance difference from goose down, but yet if we don't say they're different, it sounds deceptive because some customers will only use goose down. If we spell out the differences, studies show that more than 80% of customers don't read product descriptions and basically any written out detail, so the (largely undeserved) poorer reputation of duck down makes the product look worse, and then customers spend more money on products that perform similarly (and even if they're ours, that seems like we're trying to drive people to spend more for same performance, which looks deceptive to those who know the performance is the same) and if we use the industry standard acronyms, they look similar, and thus look deceptive.
At some point in the last year we've gone through every iteration of distinguishing duck vs. goose down, and this one has been the least controversial so far. It's not perfect, but so far it's been the best balance of being honest for the customers who care to know the difference, without being confusing for those who don't care.