Not much. Both are liposuction techniques with ultrasound. The benefit of ultrasound is multifold: it helps melt the fat so that it can be resorbed by the body. It helps when there is a lot of fibrous tissue that can't be sucked out with regular liposuction and it may help tighten the skin. Having said all that its not that new and there is no definitive evidence that it is better than regular liposuction.
VASER uses US. Vaser uses ultrasounds to melt fat which will get later aspirated. There are different catchy names given to the same procedure but the buttom line is that ultra sound is used to disrupt fat cells. This being said, ultrasound is also used in non invasive devices to disrupt fat cells which get absorbed by your body. Several sessions may be needed. The results are generally modeste.
Confusing... Unfortunately for the “consumer”, there are many different terms used to describe the liposuction surgical procedures. Many of these procedures are simply marketing techniques used by different practitioners. Also, unfortunately there is minimal regulation involved when it comes to who can perform these procedures and the terminology employed etc. Patients need to do their own due diligence.