Hi Mustang19,
Welcome to Thunder’s Place. This is the default right forum when you are new.
The vagina is very flexible, at rest it’s around 2” long, so when a woman talks about deeper or feeling fuller it’s probably about what is being pushed, stretched or manipulated by the penis. Women often talk about larger girth being providing more noticeable pleasure, which may also be in part because more care must be taken with length because it can be used in a way that hurts much more easily. Also the majority of nerve endings are at the mouth of the vagina. That said, length is often appreciated. It’s a sensible question and this is a third party perspective.