Fat transfer and stem cells - is it better?

You are correct - the fat which is transferred has the stem cells. There is no need to add additional stem cells which may be of little use anyway.

Every 10 cc of fat already has one million stem cells. So you are totally right. Some doctors will tell you they add stem cells but actually do not because they include in their calculus the stem cells are already included in the fat. While there are machines that do isolate stem cells, there is no real good literature showing that it improves fat survival or longevity. Some doctors will add platelet rich plasma, such as myself. This is rather easy to do and may help fat survival but again, there is no real good literature to support that either. The most important consideration when choosing a plastic surgeon for fat transfer is experience and a good photo gallery that shows their results consistently.

Your question is actually quite complicated. Stem cell-assisted fat grafting typically concentrates the stem cells by taking a portion of the harvested fat, separating out the part where most of the stem cells are (stromal vascular fraction or SVF), then adding that to the fat that will be grafted. There has been a lot of marketing hype using terms such as "stem cell facelift" which are very misleading. Other options include adding PRP, or concentrating the SVF with filtration rather than centrifuge. Comparisons are difficult because there are so many different ways of doing it, and it also depends on where the fat was taken from, where it is placed, and how much. More about it in my Biohacking Longevity ebook.