I avoid synthetic fabrics like the plague except for my gear, my base layers for work (my work destroys clothes because bleach so I don't invest), and my work pants (again, because bleach). Synthetics make me feel like I am suffocating in all this heat and humidity. Synthetics also just hold odor like nobody's business, and led to the great dryer sheet showdown here at our little fledgling intentional community. DH's best friend swears by technical fabrics for the Texas heat, something about wicking abilities, and his wife was using tons of fabric softener and dryer sheets to try and get rid of the stink in his clothes, IN THE ONLY WASHING MACHINE ON THE PROPERTY. I have allergies and the exhaust from the dryer was KILLING me, DH hunts, we're supposed to be being eco-friendly here, and it got nasty because she would not stop using dryer sheets with all that medicated goo that they're loaded with and I finally exploded and scorched the earth and she stopped for deer season and started back up again when it was over. She said she was just trying to get the stink out of her husband's clothes and I told her if he would start wearing merino wool and quit wearing plastic clothing (the woman believes that plastic is Satan) then his clothes wouldn't stink and she quit asking me for laundry advice.
And now DH and I have our little house finished and it has our own washer and dryer, and once any of my synthetic fabrics stark stinking then they go to the textile recycler and I replace them because it's a losing battle to try and de-stink synthetic fabrics once they've found a stench to hold onto.
Some people swear by synthetics for their gear, and I can see that it would definitely help the body retain warmth in cold weather. They're supposedly great for leggings and workout tops, but I really hate them because they trap heat and that sucks in Texas. I only wear them right now because I needed workout gear quick when I hired my trainer. As pieces wear out or become too smelly, I will replace them with rayon from bamboo or thin cotton pieces designed for the gym.
However, i am going to hop on the vinegar bandwagon here. I once watched a woman save almost all of her family's clothing after a house fire (the smoke stains, the smoke smell, it was rough). She used vinegar in her washer. She had nothing to lose if it didn't work, and vinegar is cheap, so she tried it; it literally saved them a fortune by saving almost all of their clothes. So vinegar in the wash is apparently a powerful thing, and I have used it on DH's smelly work jeans and tees with success.