I love the sheen of rayon which I often use, I also use polyester.
No preferences.

I have both but usually use polyester as I make a lot of baby quilts, burp cloths and bibs, and want to be sure of colorfastness, as well as being able to be bleached.
The poly threads sheen has gotten better too.

I prefer polyester. I use Floriani but mostly metroemb.com - have all 166 colors and love it.

I use both. Depends what I am doing. Probably prefer polyester.

I use polyester as the rayon seems to give me a lot of trouble.

Polyester by far.
It keeps its colour for all tableware and pillow cases,which are laudered often.
From Bev

Polyester! I use Sulky but was given a assorted box of Maderia. Sulky is my favorite. I started with Sulky more yrs ago than I would like to admit and I was always astisfied so did not change except when I needed a color very badly and could not get the Sulky. I lived in a rather rural town and got all of my supplies in Augusta, Ga at the time and it was almost an hour's ride. I did shop in Macon, Ga when my Mom was still with us which was a longer drive but got to see my Mom. My very first Embroidery Machine came from Macon from the Singer Dealership. It was one of the first(maybe the first) of the home use embroidery machines on the market. I still use it and it has a beautiful stitch but it is harder to use than than my 2 BabyLocks so unless it is necessary to get a design that is on a Singer Memory Card, I always go the Babylocks. One Babylock uses a memory card only and the newest one uses a memory card and just a plain old floppy disc straight out of the computer! From computer to the machine is much cheaper and easier. The sulky thread is used on all machines. I do have Sulky mettalic but rarely use it. I wind my own bobbins and everytime I walk in the dealership they fill up a small bag full of bobbins and give them to me. I have never bought empty bobbins either.

I use Rayon the most. I have used some polyester though but very seldom.

Polyester, I love the Metro great thread , colors are vibrant and many shades, price is the best anywhere.

Polyester works best for me. The colors do not bleed and ruin your project.