I can't stand toy materials that smell or sweat. If it leaves my hands greasy, it's gross. So jelly and Sil-A-Gel are out for me. I'm not too sure about UR3. Only two materials have made me outright gag: UR5 and whatever jelly mixture the Penis Scratcha vibe is made of. For each of those, I barely had the package open before I wanted to puke.
And perhaps Sil-A-Gel itself is odorless. According to the packaging, it is used as a coating layer on the toys. Regardless, I've smelled PVC toys, UR3 toys, and Sil-A-Gel toys, and they all smell different. So it COULD be the Sil-A-Gel reacting with whatever else is in the toy that makes it smell different from other materials. But Sil-A-Gel also sweats (worse than some jelly toys I've seen, yuck) so perhaps smell is a sign of it breaking down? I don't know. I'm not a chemist, nor do I work for Doc Johnson. All I know is Sil-A-Gel toys smell, and they have a distinct smell. I can open a package and tell if it's a Sil-A-Gel toy without looking at the label. And no, the smell does not wash away or air out. I had one for a year that smelled just as strongly as when I bought it.