In most cases, they are not as good as OEM. The fit although better than years back is never quite the same. Yes, the average person might never be able to tell but it bugs the crap out of me. Headlights tend to fade quicker and I have had problems with aftermarket hoods wanting to rust on the seems under the front edge as little as a year after putting them on. Don't get me wrong I use a lot of aftermarket parts they have there place. But I have had problems throughout the years, bumpers peeling (primer from the factory peeling from the cover) lights fading and rust. However, I will say I have never had any problems with a/m radiators and condensors.
Stay away from any reconditioned bumpers I tried one on my wifes equinox and it took me 3 to get one that was useable then 2months down the road the bondo they used to recondition it started falling out.