Would I benefit more from a sliding genioplasty or a chin implant? (photos)

Without an exam your question cannot be answered.  You will need to see an Oral/Maxillofacial surgeon to see if othognathic surgery, genioplasty or using an implant is best for your specific case. It should be noted that patients with severely weak jaws or abnormally functioning jaws may be better treated with other facial surgery (orthognathic surgery), although a chin augmentation may be an option at a later time. These patients should seek the advice of a plastic surgeon to determine which course is right for them. Here is some information to help you make this decision: Candidates for Chin Augmentation - Patients whose chin profiles are weak but have normally functioning jaws are candidates for Chin Augmentation. Many of these candidates have used injectable fillers in the past to strengthen the protrusion of their chins, but are looking for a permanent solution. If you are one of these patients, then you are a likely candidate for chin augmentation

Never ever recommended a chin implant, they are unstable overtime, lead to poor results in many cases, are unconfortable or painful, and of course their lifetime as implants is limited in time. For those reasons and other the osseous genioplasty (beware! calling it sliding genioplasty is an abundance of simplification, since you can not only "slide" the chin) is the choice, outweighing the implants in all fields. 
As mentioned before, the osseous genioplasty is a very versatile technique, allowing to slide, augment or reduce the 3 dimensions of a chin; that is why there are one, two and three-dimensional genioplasties, and they can be of advancement, reduction or augmentation, even mixed combinations of the formers. In good hands the results of osseous genioplasties are awesome, natural, everlasting and safe.
This is particular relevant in your case, and very easy to understand even for lay observers; your chin suffers overall microgenia or hypoplasia, this means it is too small in all them three space dimensions: too weak anteriorly, too short vertically and too sharp/narrow horizontally, thus needs a three-dimensional augmentation to lenghten vertically, broaden horizontally and advance anteriorly, namely a full expansion, to which bone grafting is required, with spectacular results. If only an advancement sliding gesture is done you'd get a weird, fake and too sharp result; needless to say just a chin implant would be disastrous. Additionallhy the horizontal broadening would provide restoration to the missing fullness and both sides of the chin, and mascunilize your look, as well as preventing a witche's chin (over sharp).
Finally, let me suggest a combined nasal procedure, it seems you have a shor-nose syndrome in need of nasal lengthening (septal extensions, caudal extension grafts, etc), and an overly rotated tip needing lowering of the nasolabial angle.
Yours is a master's case, requiring top notch skilled surgeon, expert in such specific procedures (three-dimensional augmentation genioplasties and nasal lengthening are difficulty 9 out of 10 in primary cases), used to deal with facial plastic surgery and with a very good aesthetic judgement; do research well.Note: unless some surgeons may believe, osseous genioplasties do have no connection or effect on dental occlusion issues, for such problems exists the orthognatic surgery, such is a basic conceptual confusion requiring knowledge refreshment.

Given your young age, degree of horizontal and vertical chin shortness and your deep labiomental fold, a sliding genioplasty would be a preferred choice over an implant in the long-term. The only missing piece of information in your case is what you look like in the front view which is also an important perspective for chin augmentation as well as the effect of a sliding genioplasty and a chin implant will be different.