Polyester is far easier to use when compared to epoxy. Epoxy cures very slow, which sounds good, but it also tends to drain out of the glass as you're waiting, so you need to fiddle with it until it hardens to the point where it will stay put. It also doesn't wet the glass out as easily, so that part takes more work too.
In hot weather some polyesters cure very fast, which can catch you by surprise at first, but you can get used to, or work when it’s cooler. Epoxy will be slower curing if you use the slow cure hardener, and will eventually cure even at very low temperatures, so in some ways that can be helpful.
Epoxy does bond better, so people feel if they do something wrong it will have a better chance of holding up, which is true, but they both require the surface to be sanded for a good bond, so just sand it well.
The odor of polyester can be very annoying, and it can be detected by your nose at very low levels, far below what’s allowed in a glass shop for working in every day all day long, so the health aspect isn’t that bad. But, while working with it in your garage the entire family will hate you because of the smell, you aren’t doing them any damage though. Any food or other things kept in the garage will take on the odor, some hold it for a long time, others don’t, and you won’t be able to smell it, but other people will, which can lead to some strange looks when you’re in a restaurant or store. Any food kept in the garage will be spit out on the table after the first taste.
Epoxy can cause severe health issues, although if you keep it off your skin you’ll be fine. And it’s only some types, not all, it’s hard to tell which is and isn’t a health hazard though. It typically doesn’t smell, so people won’t even know you’re using it.
Really what it comes down to is that in the average rebuild it doesn’t make much of a difference in which resin is used, both will hold up just fine.
