I haven't used the HOG backplate and harness but I have used the wing (32#) with a double-hose regulator setup. It works well.
A harness is just a piece of webbing with some gadgets threaded on. Not much to talk about there. Other than the Freedom or DSS offerings, plates are plates. A piece of metal to which the wing and web are attached. Or, in the case of the OxyCheq UltraLite Travel Plate, a piece of fabric or something. There may be some other plates with somewhat different features but I haven't used them. DSS, for example, offers a Kydex plate.
Now, the DSS plate is a work of art with the elastomeric grommets at the web slots and the Freedom plate has some unique characteristics as well. But if what you want is a standard 6# SS plate, there isn't much to differentiate them.
All of which points out that a BP/W is just a collection of parts tied together. It just doesn't matter which pieces you choose. Sure, you can get into long discussions of inverted U versus toroid wing construction, you can discuss how much lift, you can look at various profiles but, at the end of the day, they are a bladder that holds air.
The OxyCheq Mach V, the DSS and the HOG wing don't need Single Tank Adapters to keep the tank in place. The DSS wing has the best support blocks (in my opinion) but the other two have ridges to align and support the tank. Other wings may have a similar feature. In the end, the tank bands do most of the work.
There is a feature to the DSS wings that is worth considering: the wing is not captured by the tank bands. Further, it isn't bolted to the plate either; there are little elastomeric nipples that push through the holes in the plate. You can simply pull the wing away from the plate and store it separately. This may help prevent damage.
I like the HOG wing. But I like my DSS rig better. It's just that when I want to use a double-hose regulator, the center outlet of the DSS wing gets in the way. If it weren't for that issue, I would have never looked at any other wings.
Richard