I recently purchased a Horze quarter sheet and although its probably not as warm as polar fleece, it is made nicely, has a waterproof exterior and does not create static. Plus with the Horze 50% off codes, the price is hard to beat
I've found coat length to be a major factor.
My full clipped guys usually have non, but my trace clipped ones can have some even when brushing.
Although speaking just of QS's the imported wool newmarket never has static on any hair coat,but the fleece ones usually do.
The regular fleece ones I have crackle with static. I do have a couple made from some kind of Malden Mills technical fleece that they make human clothes from and they don't get the static like regular fleece for some reason.
I find that I have much worse problems with static with polarfleece and other synthetics, so you might want to try a wool quarter sheet. That said, you can also try dryer sheets or Static Guard - I think they are both a must have at the barn in winter :-)
Static Guard is the only way to go with this stuff. Lay your quarter sheet (or blanket, or whatever) on the ground with the horsey side facing up and spray, spray, spray that thing. Wait a few minutes and then it should be good to go! I spritz my blankets once a week to refresh everything and just to keep the static to a minimum. It comes in a blue can with an orange top.