I just received some super cute decorative pillows for a client yesterday and like many companies, we were able to choose whether we wanted down- or polyester-filled inserts. 99% of the time, I will suggest down/feather inserts. And here’s why…
Down (or feather, or a combination of both) is going to give you the fullest, most pliable pillow. You can mold it, shape it, do the karate-chop finishing touch on the top and it’s going to stay that way until you change it again. It’s soft and squishy and just really fills out your pillow cover. If your cover is a little large, you can bump your insert up to the next standard size and it will form nicely to the corners and not look over-stuffed.
Polyester is fine for some applications. We ordered a wool pillow that was very heavy and the poly insert worked just fine because it filled the pocket tight and held up the thick cover. Some people are worried that their pets (dogs especially) will tear up a down pillow, or that they will be allergic to the natural inserts. Polyester is OK in those instances as well. But, you’re just not going to get that full pillow look with a standard polyester insert.
True, polyester inserts are generally less expensive, but you can easily find feather/down inserts for a reasonable cost.
My take-away: choose down or feather any time you can. They will look and feel and perform better for the long haul.