Height plays a factor as well. I am average size and I dated a short, thick girl back in 2010. She was convinced I had the biggest dick in the world. When we had sex, no matter the position I always dick-punched her cervix and she would push me off.
I also fucked a girl, who was slim with some huge tits back in 2008. She thought I was huge too. The sex was "meh" because we had a wack ass condom, then it broke and she wanted to keep going.... So she got on top and we fucked raw. I hit her cervix as soon as she sat down and we both moaned loud. I swear that was the warmest, best feeling I have ever had while having sex. I bust so hard I got a headache. If she didn't move out of the way when she did I would have a child right now. That was the best orgasm ever.... lol
Sorry for the rant, it just depends on the girl and her experience lol. Mostly depends on how you make them feel once you are inside... because I dated another skinny girl in 2009 and she didn't think I was that big, until I put her legs on my shoulders and starting diving in that pussy lol "it hurts, it hurts!!!"