I have used both Reaction and Velashape. In terms of full disclosure, I was an investigator for the clincal study that helped Reaction achieve FDA approval, but I do not receive any monetary rewards from the company. True, both systems use radiofrequency and vacuum and some would argue that there is not a big difference between them, but I think there is a key difference. Reaction allows for the radiofrequency to be changed, thereby changing the depth of penetration, making Reaction is the only multi-frequency RF device on the market. Why is this important? Because the depth of penetration is crucial to what you are trying to treat. if I am targeting fat, I want the energy to go deeper than if I was targeting skin. In my experience, this more specific targeting allows for good results with low risk of injuries such as burns. There have been no head-to-head trials between Velashape and Reaction, so no one can really answer which one is "better." In my opinion, I find that Reaction allows me to perform skin tightening, cellulite reduction, and fat reduction predictably and with very good results.