Let's just jump right in and state the truth: men think the length of their penis is important, and women think GIRTH is important. Long is only necessary for PORN so the camera can see the action while the penis is still 'inside'.
Now that we have that out of the way, let's talk about what each penis size is good for. Let's state penis size by LW (Length then Width), where the L can be s:short; m:medium, l:long, and the W can be s:skinny; m:medium, t:thick. So a "short length, with a medium width" would be an SM. MM is roughly "average" penis size (5.5-6" in length and girth circumference is roughly 4"). Significantly shorter is 'short', and significantly longer is 'long'. Same for much thinner (s), or much thicker (t).
In this discussion, "short" and "skinny" are in no way a pejorative, so do not be worried about the size of your package (or your boyfriend's package). Just be honest with yourself about what you think your length/girth are, and you will find yourself a happy camper!
Let's start with short. A SS penis is perfect for giving G-spot orgasms. If a woman is lying on her back, just inside the vaginal opening, if you push 'up' (towards her belly button), is the area where the G-spot usually is. It is before the cervix (which is also 'up', and feels like a stubby round thing). Most women have a single G-spot, and it is either right in front of the cervix, or off to either side. Some women actually have 2, one to either side. A short skinny penis is PERFECT for hitting the G-spot... if you have had your fingers inside of her, and have found the spot that makes her moan, then when you begin having PIV sex just try to angle for the same area. A SS penis can angle around to find the spot. You want to try "massaging" the spot with the tip of your penis, and try "tapping" it, and see which gets you the better response.
A SM penis, having a thicker girth will have a bit harder time finding the perfect angle. It is just a little more difficult to maneuver in a tighter space, so to speak. You can try bringing her legs up or down to try and shift the vaginal wall for better access to the spot.
A ST penis is often best with the woman on top. Behind the cervix is the kegel zone. Having a 'full' feeling right behind the cervix can allow for a woman to 'bear down', and have a kegel orgasm. (I will explain the 3 different zones that can trigger an orgasm in women's vaginal areas, in another blog post, along with the different TYPES of orgasms a woman can have). With a ST penis it is difficult to maneuver much near the opening, but you can change the angle enough to shift where the tip ends up. You want it to be right behind to cervix, if possible, which is often easiest to do with the woman on top, and she can 'grind' the penis into the right spot.
A MS, the same is true as for the SS, except that you might need to not push all the way in for you to be able to hit the G-spot. G-spot orgasms in women coveted so if you can find the spot, and keep from pushing past it, you will have a very happy lover.
MM can try the MS/SS style, and can try to ST style, but can also just try the plain old 'in and out'. MM is often a good size for most women, can try hitting all the different places, and generally have good results.
MT also wants to aim for the kegel zone, but can probably get to it from more positions than just the woman on top.
Long penises can be VERY problematic for women. That does not mean you should be neurotic if you have one, but it does mean that extra care needs to be taken. The inside of the vagina is somewhat 'heart' shaped. The entrance to the vaginal would be oriented at the bottom of the heart, and if you imagine the penis coming up, and into the heart, it will hit the center 'peak' at the top center of the heart. This is where a woman's bladder is. If you _bruise_ this area she will get a bladder infection and will be unable to have sex for a month. Nobody wants that to happen.
Invariably men want to have long penises, and women do NOT want men with long penises, because it is often difficult to let a man know that he is hurting her, without ruining the mood. If you have a long penis, you need to be conscious enough to _angle_ so that you do NOT hit the center. To either side of the enter are 2 deep 'pockets' (the rounded parts of the heart). If you enter her and move so that you are slightly off-center with your thrust, it will push the penis off to one side or the other, and you can get deep. Once in there deep regardless of whether or not you have an LS/LM/LT you can 'grind' into her a bit, and if she bears down, she can have a kegel orgasm. It is NOT about pounding, it is about 'massaging'. The pounding, for some women, can raise the passion level, but usually isn't what triggers the orgasm.
Keep in mind that these are generalizations, and if a woman you are having sex with tells you to do it different, then do as she requests. Nothing stated here is meant to be the answer to EVERY woman. Sadly it just doesn't work that way.
I hope this has made you feel more comfortable with the size of your penis (or your partner's penis, as the case may be).
All comments are moderated, so feel free to ask your questions in the comments section. Your question, along with the answer, will be posted without your identity being disclosed (unless you request it).