What's the pros and cons of liposuction under general anesthesia and local?

As with all things, there are trade-offs.
Local-only liposuction allows patients to avoid any side effects of general anesthesia (nausea, blood pressure swings) and the cost of an anesthesiologist. So what are you trading? Comfort and likely results. First, comfort can be a challenge with local anesthetic only. More numbing fluid must be administered and it must be administered slower, which can increase the operative time. Although most people can tolerated the procedure, some cannot, and I do not know anyone that has enjoyed the procedure. Additionally, I cannot be as "aggressive" with my fat removal with an awake patient. 
For smaller areas or targeted liposuction, local can be used effectively. For larger liposuction procedures it is my preference to have general anesthesia or at least IV sedation.

Lipo can be done under local (often with some oral sedation) or general anesthesia, depending on the areas being treated, surgeon technique, and other factors. The general advantages of local are:1. No need for general anesthesia, with less risk of blood clots in theory2. Patient can move around and change positions (including being upright in some circumstances) to allow the surgeon to see possible differences with gravity3. Recovery is faster in terms of not needing to overcome side effects of general (nausea, drowsiness, etc.)However, there is a risk of lidocaine toxicity which requires a clear understanding of maximal volume of local anesthetic that can safely be used, and this may limit how many areas can be treated in one surgery. This in turn may result in needing more than one operation. The surgery also may take longer because the surgeon may not be able to be as aggressive and may need to stop periodically to assess your comfort and add more local. I find this tedious for large areas and believe that general anesthesia is preferable for large areas and BBL/fat transfer cases for sure. With general anesthesia, I can be very aggressive and get a more impressive change. Some dermatologists and other specialists who are not actually plastic surgeons may not have facilities/resources for general anesthesia and in such cases, local will be the only option.