Mine aren't made of either - mine are saline and under the muscle. A lot of people don't notice them (I think almost half my reviews state natural breasts) because I used to be large chested, so all you feel is the REAL breast tissue and the saline is merely holding it up for you
That being said I got implants for that exact reason - I had a LOT of natural breast tissue from when I was naturally a DD (largest size was F) as a teen/young adult. When I got into shape I lost allllllll of my breast fat and simply decided to replace it. My implants feel as good as they do because I used to be naturally large. My nipples are the right size to be on larger breasts.
What do I like on a woman who has never had large breasts? Just depends on her body. I love the feel of well done implants, but natural boobs are amazing. My absolute favourite type of breast is the somewhat large, natural, and slightly low hanging (NOT SAGGY) breast of a woman in her early 30s. Mmm.