In a backplate system, quality of the wing very much is just how they are put together and grade of material. Design of wings, new or old design, IMHO, it's not going to make too much difference. I think depends on what 'school' of diving you are into, configuration of dump valve, elbows, hose length maybe more important.
D-rings and fittings, usually are just 316 stainless steal. I can't see significant difference between those brands. I think the main difference is quality of backplate. Material and hot they are treated can mean significant difference in terms of quality and durability. Some backplate corrode really quickly and others are soft. The difference will be obvious when u start carrying doubles.
As for STA, I dive with them, I feel the setup is more 'proper'. But STA do drive up cost and a heavier package to travel with.