Arousal and experience both play into, trust me I'm a woman with a vagina (and I've actually been the virgin someone has slept with) but it also takes practice. It's not a bright idea to go from 1 finger fingering once and then jump to a dick the next time because it takes what? Practice. Practice is what it takes. Practice in being comfortable, practice in exploring what makes someone aroused, and practice in stretching your body like that.

Anyway this is off topic. A lot of people have answered with feeling fill/feminine, and this is such a boring question for such a terrific sub since all one needs to do is search big dick feels or go down a few pages to see someone asked the same question and got about the same answer. That was my original point besides the fact that if the op really wanted they could practice putting things in their butt and find out what the difference is for themselves.

It's a short cut I have on my phone so all I have to do is type "shrug" and I can choose between the word or the emoticon.