Silicone is more comfortable but foam offers more NR. The silicone ones also get dirty and nasty after a while. But that was when I had pre mix and oil stained fingers putting em in too. I just use foam, they're easier. Custom molded plugs are the best way to go but that's a lot of extra futzing around.I have to try the silicone reusable ear plugs.
I use the foam ones but they are a pain in the ass if you want to take them in and out.