What is better, BodyTite vs J-Plasma for abdomen loose skin tightening after weight loss?

Hi, thanks for your question! One of the most important differences between the two is that with BodyTite, the surgeon can see amount of energy being used and the energy emitted is limited for patient safety, and with J-Plasma the energy is not controlled or limited. Since there are no controls for the energy with J-Plasma, risks of burns are increased. And since J-Plasma is fairly new, most surgeons do not have enough experience using it to ensure the correct amount of heat/energy is being used per area.

Hello, thank you for your question. You probably need some sort of skin removal to be happy, but this really just depends upon your expectations.  BodyTite is a non-excisional device that utilizes radio-frequency assisted lipolysis to address the shortcomings often associated with traditional liposuction or surgical body and face lifts, including sagging or wrinkly skin and scarring, by inserting a wand under the skin to coagulate inside while tightening the skin on top. 
While a traditional TT can do wonders for your body, it leaves a large and unwanted scar behind. At Hughes Plastic Surgery, we offer a better option: the short-scar TT.
A short-scar TT was developed to enhance a patient’s abdomen and get rid of excess fat and skin in a way that created more attractive results. The shorter scar it leaves is the same length as that of the mini TT.  While the mini TT is less invasive, it also isn’t as comprehensive as the full TT. A short-scar TT, however, offers double the amount of loose skin and fat removal that a mini offers. Schedule an email, Skype or in-person consultation with a board certified plastic surgeon.

if you have really loose skin you will need skin removed. if there is little loose skin internal heating can give improvement. 
You need a formal evaluation by an expert in body shaping and contouring to determine what is best.  Traditional liposuction awake and smart liposuction are old methods and do very poorly for tightening skin or significant skin tightening or contouring.  Small problem areas can be improved slightly by these methods.  The best in body contouring not only removes fat with energy devices like VASER ultrasound but also internally heat the skin with radio-frequency devices such as J PLASMA/RENUVION, InMode BodyTite, ThermiRF to heat the under surface of the skin and tighten it at the same time as fat removal. These combinations are called 4D HIDEF VASER contouring and can only be done by a well . trained body contouring specialist. At the same time fat should be harvested, PRP and stem cells added and injected into muscles or indentations/cellulite to get body shaping and contouring.  This is known as a Brazilian butt lift when you inject the fat to the buttock for contouring and lifting, but fat can also be used in areas such as the chest/breast, arms/shoulders, calves and face.  Cellulite should also be treated with cellfina, sculptra, subcision and/or fillers such as bellafill, renuva synthetic fat, or sculptra.  If skin is very loose before surgery then it will need to be removed such as lower abdominal skin (tummy tuck/abdominoplasty), breast skin (breast lift), arm skin (brachioplasty).  Overall you need a full assessment, but simple liposuction alone will not tighten skin and needs a combination of various methods -- fat removal, skin tightening, defining, fat grafting, skin removal -- to get the best in body contouring and body sculpting.  Dr. Emer.