Dr. Posner likes to do these procedures together. They work on different areas of the dermis. Halo is more superficial and helps better with the fine lines but Infini as helps those. The Halo is a workhorse for pigmentation problems. Infini is for tightening, scars, deep wrinkles. Halo won't help with sagging at all.
Halo and Infini RF are both excellent modalities for overall improvement of skin concerns, but they do not achieve the same end results. I use Halo for skin where there is pigmentation, coarseness, large pores, mild acne scars and fine lines. Halo does little for laxity of the skin and has limits on severe scarring and lines. Infini RF on the other hand bypasses the surface of the skin and delivers energy deep in the dermis resulting in collagen repair and replacement more than doing anything significant to the surface. It therefore is the tool I reach for when there is skin laxity, acne scars that have associated laxity and where I do not want to deliver energy to the surface and run the risk of damaging darker skin tones. Does it improve coarseness and pore size over time? Maybe a bit just by induction of new collagen, but I don't reach for Infini when those are the main concerns.
In my opinion, you would benefit from a full face infini. It should help the loose skin underneath your eyes as well as tighten the jaw line and neck. The one area I have not had much success with tightening is the cheek area. Infini produces rejuvenation of the skin. Regarding your neck, based upon the photos, I don't know how much of the muscle is involved. There may be some advantage to pre treating you with Botox prior to doing the Infini in this area. Find someone who has experience with Infini. Ask to see photos. Hope this helps. Good luck.