Poly is really soft, does not wear well. Nylon is better for carpet runners....yes. Wool is considered best...like you said...it's the most expensive. Go for low pile and high density in a carpet runner.

Good quality + wool IMO is the best. Others can contribute to VOC's. Outside of that, generally nylon is the next best for durability

Here is a link that might be useful: VOC's

Have you priced wool lately? I've found some really nice wool carpet for less than nylon carpet at Carpet Liquidators. I don't know if they have CL in your area? In our area they carry huge rolls of wool carpet...just an idea..

I used to have a plush oriental-style nylon stair runner, nice and thick but with a dog in the house it was a nightmare to keep clean. I'd have to get a damp washcloth and go over each tread to scrub the dog hair into a ball before I could vacuum it up, it took forever to do right and was a chore I dreaded. When we had our floors/stairs refinished last year the techs weren't able to remove it without ruining it - the PO's nailed the crap out of it when they installed it. I needed to replaced it in a hurry - besides the dog I have two young boys and was worried about them falling down the long straight run. I went to Home Depot and got the 'el cheepo' runner-on-a-roll as a quick fix and stapled it on. I've never replaced it - it's thick enough to cushion falls and vacuums like a dream - I use the soft brush attachment and it lets go of everything. It's also worn like iron. I will even confess to going back for enough to do a runner for in front of the front door and upstairs hallway - I folded over the raw ends and duct taped it into a hem!

Money $aved for other goodies!

I actually think the blue runner they put down is from Home Depot. It's polypropolene. I know nylon is better and of course wool would be preferable, but this ugly blue runner did actually wear like iron.