I frequently get asked which of the male genital piercings is the best for providing additional stimulation to a female partner during intercourse. Or, as it has been more crudely (but clearly) put to me, "Which cock piercing is going to make my girl scream with pleasure when we're f*cking?"
As with many things, there is no one-size-fits-all answer.
I'm willing to divulge that my personal favorite is the apadravya for g-spot stimulation. I've even done some of these on dildos for women who didn't have male partners but liked the added sensation from their toys!
Note that your sexual fit as a couple is an important consideration as to whether a piercing on this part of the penis—the glans—is a good idea. If a female partner is experiencing soreness due to your size and/or lovemaking style (roughness or duration of intercourse), then adding jewelry in this region may not be fun for her, nor helpful for your sex lives. And such a penis piercing is definitely going to cause issues if you already have a too-snug fit because it adds to the dimensions of the area. The post portion of a barbell should fit the tissue end-to-end when you're erect, but the jewelry will extend beyond the surface by the size of the object on each end (most commonly a ball, though flatter "MnM" ends can be worn for a lower profile).
If, on the other hand, there's some ease between you, then wearing jewelry through the glans could be just the thing to improve your fit and add sensation for both partners! The ampallang would also function this same way—especially when placed at the widest part of the glans. And, of course, either horizontal or vertical piercing has the potential for g-spot stimulation depending on the angle of entry.
Speaking of entry, to facilitate this, I normally angle apadravya piercings with a slight lean (usually backward), though this is not an option for the ampallang.
Though the Prince Albert is a very popular piercing among men, I know that some women feel them and others don't—unless the jewelry is quite large. So that may be one to select more for yourself than for your partner. Frenum piercings are another spot that may or may not make an impact during intercourse. This depends on several factors including your partner's sensitivity and your fit together, along with jewelry size and piercing placement. The frenum can be worn anywhere around the shaft where the tissue is pliable, so this is quite variable.
For clitoral stimulation, the pubic piercing is the one for the job. Of course a ring needs to be worn; a barbell isn't going to have the same effect. But during face-to-face intercourse, it is possible for a ring in a pubic piercing to touch the clitoris. Still, for ease of healing, the bar is suggested for the initial jewelry, and it can be changed later.
Depending on individual build, piercing placement, and jewelry selection, midline scrotum piercings have the potential to swing and hit your partner in the right spot during doggy style action. Another thing that could add clitoral stimulation: piercing(s) for her, specifically the VCH and/or triangle.
Note that piercings shouldn't be considered a panacea for any sexual incompatibility or issues, and no piercer can make any guarantees about how much you will enjoy them. But I can say that I have a LOT of satisfied clients who derive a tremendous amount of enjoyment and satisfaction from their genital piercings. So if you're interested in piercings and they appeal to you, then it is certainly worth a try!