First of all, it is very important for all patients to know that EVERYONE has some degree of breast asymmetry. Sometimes, it may not be apparent to the patient, but often careful analysis and counseling by the plastic surgeon can help educate the patients about breast asymmetry. It is important to go over this and discuss this PRIOR to surgery. Other patients have more significant assymmetry that is very noticeable and can be very debilitating to patients.
I literally just had a patient in surgery today with a very similar anatomic description to yours.
I carefully explain to my patients what they can expect with surgery and also that they will always have some degree of asymmetry. Breasts are not ever mirror images of each other, and it's important to know that before surgery.
When one breast is significantly larger than the other, it is often more "ptotic" or droopy and the nipple position is also usually a bit lower than the smaller side. The smaller breast as you describe usually doesn't have any droop to it. In order to make the breasts more similar with implants, the first goal is to create similar breast mound volumes between the two breasts. The larger, ptotic breast will require a smaller implant and the smaller breast will require a larger implant; HOWEVER, it is important to understand that that alone will not make the shapes of the breast similar to each other. The smaller breast will have more projection and "look tighter" because the volume is composed of less breast tissue and more implant, while the larger droopy breast will still look droopy with a small implant in place. That is really all that any surgeon can do with implants alone.
There is one more thing that I do that I think helps a bit. I do a "dual-plane" technique that helps do some degree of internal lift on the larger droopy breast that has the smaller implant. I think this helps a bit but won't prevent you from needing the right sided breast lift. In a mild case, it might prevent the lift, but in more severe cases I don't think it will.
In my patient today we discussed all of these issues as well as the NEAR CERTAINTY that she would need a subsequent one sided breast lift to give her better symmetry; however, we both elected to just do the implants first and wait until they are fully settled into position which is usually 3 months, and then likely proceed with a one sided mastopexy (breast lift) on the larger breast at that time. I also tell my patients that they may be happy just the way they are. You may decide to hold off and come back and get the lift in several years, or never at all, but that is a decision you can make and don't have to feel rushed about making.
I think the breast lift scars are not a big deal and in patients with this type of asymmetry I have never had a patient regret having the procedure with the trade off in the positive being having much more similar shape and "uplift" to the breasts which displays well in clothing, etc. I think there are a variety of techniques with breast lift.
The other thing that is nice about waiting 3 months and then "doing part II" of the procedure at that point is that sometimes the surgeon needs to further adjust the implants. There is only so much the smaller breast can stretch in any one surgery and sometimes it is necessary to remove the implant from the smaller breast and place a slightly larger implant to "catch up" to the other side. However, in any breast lift, the breast oftentimes will be slightly smaller as well.
I think it is most often necessary to do the the best asymmetry correction in severe cases in two steps. Even then there will still be some degree of difference, but this will be substantially better than it was before and most patients are very happy. Yes, there are some incisional scars on one breast for the one side breast lift but that is a small trade off that is necessary to get the shape of the breast more similar.
I have never had a patient regret incisions if that was necessary to improve shape. The only scar that you will likely see will be the vertical limb in the central lower breast. The periareolar incision fades well into the areala and the inframammary crease incision is hidden below.
I hope this helps!