Some silicone has more drag to it than others, but every glass toy is unyielding because it's hard. You can do temperature play with glass and not so much with silicone. Silicone can sometimes retain smell (depending on quantity of silicone in toy), but glass never does.
You'll have to try and see for yourself. I was scared of glass because it's so hard, but come to find out I like hard in certain places.