Vaser vs Vaser High-Def ~What's the Difference?

The different levels of techniques used with VASER really just describe whether you remove bulk or whether you contour and create and definition.
So having just VASER would suggest just bulk reduction.
Medium Def and Hi Def suggest the will be some for of contour and definition.
Best would be to tell your surgeon what you are expecting and then ask them to show you pictures of their previous patients and results.  You both need to be singing off the same hymn sheet or else your expectations will not be met.

Hi there. VASER and VASER Hi-Def are the same. I see you asked this over 20 years ago now I'll insert our definition of VASER just in case someone else has the same question.

VASER high-def liposuction, sometimes referred to as liposculpture, is an innovative procedure that combines multiple technologies and tools to melt and permanently remove fat. Using the vaser technique, we are able to precisely sculpt and contour the treatment site. VASER lipo utilizes a specialized tumescent fluid and ultrasonic energy to first liquefy the fat cells, maximizing fat removal. This minimizes damage to the surrounding tissue, less blood loss and allows for a shorter and more comfortable recovery with less bruising and swelling compared to traditional liposuction. Furthermore, the incisions and cannula used in VASER liposuction are smaller than those used in traditional liposuction.

Some studies show that there is less injury to the body with Vaser than with traditional #liposuction. Recovery from Vaser Liposuction is based on the level of soreness and bruising experienced by the patient. But, it can vary among patients. As with traditional liposuction, there are no large incisions  or effect on the muscle and other underlying tissue. Therefore, #healing time may be less than anticipated by most. Hence, patients may experience less #pain or discomfort, #swelling (#edema) and bruising post procedure due to the nature of the technique.  
There are three types of #Vaser Lipo. Each benefit patients differently depending on their needs. Vaser Lipo  is capable of removing fat from resilient areas providing a smoother and slimmer results. It is common for reducing love handles, extra skin along the bra line or flanks on many female patients. Additionally, it is often applied to the reduction of male breast surgeries, called gynecomastia surgery. Meanwhile, Vaser Hi-Def  targets both deep and superficial fat cells which is found around muscle tissue. This is suggested to tone and defined rather than reduce fat when not necessary. Finally, Vaser #4D, although similar to Vaser Hi-Def works well with the existing muscle tissue.. However, it results in more natural appearing definition to those areas, being treated. Vaser 4D is often applied to treating abdominal region to improve definition.  Additionally, it's not uncommon for Vaser Liposuction to combined with fat transfer which removes and transfers fat to another area of the body. A candidate for Vaser Liposuction is a person in good health who seeks a minimally invasive way to remove stubborn fat with less downtime than traditional #liposuction.  Vaser is ideal for those seeking improved definition of muscles and contouring.  Those who seek increased sculpting of are ideal vaser lipo candidates. It's best to begin consulting with a board certified plastic surgery to learn if you are a candidate for liposuction. If so, you will then learn more about which #technique will work best for you and your goals. It is important you select a plastic surgeon who is #board-certified and has a great deal of experience with #vaser #liposuction.