First of, I have to say I am pretty skeptical of this whole topic. Experience would tell me that I am capable of both really intense and pleasurable and really, really bad sex with the same penis. Counting nerve endings seems a bit superfluous.
As far as what does matter, we need to remember that there are a lot more nerve endings in the brain that in the penis. This comes into play with psychological issues. For instance, the first few times I take out my cock in the presence of a new partner, I feel comfort that it is not small. After these first few times my dick is just my dick and neither of us will generally have any reaction to its size.
From a physiological standpoint, someone hinted at on element that matters (at least to me). Guys always talk about a woman having a tight box. At nearly 6 ½ inches around, every vagina I have ever had the pleasure to enter is tight. In fact, aside from the obvious pleasure of giving and receiving orgasms, one of my favorite physical sensations is working through the initial penetration. Give her a little, she wriggles around and gets comfortable, repeat. (If this is accompanied by an Oh my god, you are so fat, all the better.) Even after 15 years, my ex-wife and I still took our time on that first contact. Plunging it all the way in is of no real use to either party and wasting an opportunity in my book.
One other thing that comes to mind is the element of surprise. Weve worked the concept of a womans first reaction to death, so Ill leave that alone. As the LPSG has evolved (and we seem to get more posters that dont actually have any experience with a large penis), the focus has shifted from things you cant do easily or with regularity. As an example, I would guess a guy with 5 x 4 gets deepthroated with some regularity. While probably still cool, it is old news. It took 25 years of sexual activity until I got deepthroated for the first time, by my current girlfriend. It came out of nowhere and the jolt of electricity that went through my whole body was palpable. It was a thrill I wont soon forget, in large part because it was unexpected. It involved nerve endings all over my body, not just in my dick.
Really, you are in a lot of trouble if you are a penis focused guy during sex. A better plan is to pretty much forget about your dick and starting thinking about doing everything you can to get your partner off in a major way. This attention to detail will generally get reciprocated and, even if you only had one nerve in your cock, she will find it and make sure you get everything you have coming to you.
Steps down off the soapbox