This is a really good question and one I am asked often in my practice. We know that facial aging leads to gradual volume loss. It is this process primarily that leads to a changing facial shape and sagging. For this reason, my response is always to start with volume replacement, whether with hyaluronic acid (HA) fillers, such as Juvederm, or with so called collagen stimulators such as Sculptra. Personally, I prefer HA fillers, as in my experience, they are more predictable and reproducible than Sculptra, which relies on the individual response of each patient. HA fillers are also reversible in the unlikely event of a problem. However some patients prefer the more gradual onset of Sculptra. It works by stimulating collagen but it is still essentially a filler. It just works a little differently. We offer both in my practice. I tend to recommend skin tightening treatments such as Ulthera or radiofrequency, when there is already sufficient facial volume. These treatments are designed to lift and tighten by stimulating collagen and elastin production. They do not add volume, they tighten around the existing structure. For younger patients, I usually recommend radiofrequency treatments such as Sublime or Exilis. These patients have more collagen to start with and radiofrequency thus works really well. For more mature patients, I recommend Ulthera. Using both volume replacement, such as with Sculptra and skin tightening, such as with Ulthera makes a lot of sense, as they should work synergistically. If I had to choose just one though, personally I would always start with volume replacement. Best of luck with whatever you choose!