What is the difference between neck and chin liposuction? What would be best for a more defined jaw line? (photos)

Kybella or liposuction could improve your double chin and neck profile.  The neck and "chin" areas are probably the same so make sure you clarify with your doctor before hand.

Liposuction of the neck includes the area under the chin.  Some people may refer to this as chin liposuction and some may refer to it as liposuction of the neck, but it is essentially the same thing.  It does appear that you would be a good candidate for this procedure.  

A full set of facial photos in a chin neutral position are required to make a determination about what may be needed. A physical exam is needed to make a determination about skin tone. Liposuction the neck involve removal of the fatty deposits above the platysma muscle. A surgical neck lift is required to remove fatty deposits underneath the platysma muscle, and then a platysma plasty is required to improve the jawline significantly. For more information and  many examples, please see the link and the video below

 Hi, I have performed many facial shaping procedures using dermal fillers, facial implants (cheek, chin, lip), liposuction and/or facelifts for over 30 years.  From the photos, your chin is very weak as are the back portions of the jaw line, there is loose skin in the lower face (jowls) and neck with excess fat below the chin.  Lipsoction to reduce the excess fat alone (by any means using either liposuction, fat dissolving injection or topical skin treatments), will not correct the "weak chin" or strengthen the jaw line significantly.   
 I have performed many Chin Augmentations using silastic chin implants for over 30 years.  A weak chin creates an imbalance making the nose appear larger, the mid face top heavy and the lower face look short that de-emphasizes the lips and allows early formation of a double chin.  Chin augmentation using a silastic chin implant will add projection to the chin creating harmony and balance to the lower face. Liposuction under the chin and across the neck would be performed to further shape the chin and neck.
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty.  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  In my opinion, you are a good candidate for chin implant surgery.
 The back portion of your jaw line is a bit weak and can be augmented, without making your face appear masculine, using precise placement of a dermal filler (I prefer using Restylane Lyft).   Following my beauty principles, women look the most feminine, youthful and attractive with heart shaped faces.  Heart shaped faces have cheeks that are full and round in the front.  Cheek augmentation with a dermal filler or using cheek implants for a permanent enhancement will create full, round cheeks that will feminize the entire face.
 If you have "jowls” these are sagging facial tissues and an indication for some form of a SMAS facelift.  The underlying SMAS layer, of the face, must be dissected, lifted, trimmed and re-sutured (not merely folded or suspended with threads or sutures that will not last).  The excess skin is then removed and the facelift incisions closed.
My most popular facelift is the minimally invasive, short incision facelift that has all the benefits of more invasive facelifts (traditional, mid-face, deep plane, cheek lift and subperiosteal facelifts) but with these added benefits:
very small incisions and no incisions extend or are placed within the hair.
minimal tissue dissection = less bruising and swelling = rapid recovery ( several days instead of weeks or months with the more invasive type facelifts mentioned)
can be performed in 90 minutes or less, with or without general anesthesia
no incisions within the hair = no hair loss
excess fat can be removed
excess skin removed
cheeks, chin and jaw line can be augmented with dermal fillers (I prefer Restylane Lyft) or facial implants
most patients fly back home to parts all over the world in as little as 3 days post-op
I combine facial shaping with every facelift procedure.  When jowls are present, these should be done in concert and not alone or separately in order to create a naturally, more attractive face.
Hope this helps.

Both terms usually refer to the same procedure although some persons only require removal of a small fat pad directly under the chin. As well, the jawline depends on the support from the underlying bone; so you should realize that removal of some fatty tissue does not always result in the defined jawline; unless other management of the actual jawline is done.