that article on why a BP is better than a jacket has very flawed reasoning.
1. air in a jacket and BP/wing will behave in the same way - it will go to the highest point of the BCD and not around/under a diver in a jacket BCD, and also not flat like a sandwich in a BP/wing.
2. divers with a BP/wing will still have weights around their waist and not evenly distributed across the upper torso -- where else do you wear your weightbelt? Maybe that diagram is true if you're using a steel backplate. Most aluminium ones we use here are maybe 2 pounds negative. Not much of a difference to claim as a benefit if you are properly weighted from the start.
i use both jackets and BP/wings, and don't find any great difference in helping to maintain trim. Maybe a little more streamlined, but after adding all the pouches and 3241276512 things from the D-rings, maybe about the same. I'm using the BP/wing more because it's lighter than my jacket. But given a choice and assuming weight is the same, i'd go with my jacket BCD anytime because it's easier to put on and more comfy overall.
I think many may look at trim issue in too simplistic a way. Good trim is not just BCD, it involve skills. A good BCD may help one achieve good trim easier, but there is still diver factor and other considerations.
How IMHO a backplate can help are as follows:
1. True that air will get stuck to the highest point, but in a wing, air will get stuck much higher than a jacket styled BCD. In some ways, it does raise the centre of buoyancy and lower diver's CG. Resulting in a more stable trim position.
2. A BP BCD do help better distribute weights as at least 2lb are shifted higher upwards to the back of diver and directly under lifting wing. True that some may still have weights on our waist, as long as you are not carrying a ton of them, diver's CG do get shifted closer to the head.
The way I see it, more than 80% of the divers using BP system do not understand how to effectively use it. Most use it because friends and forums like this says good things about them. In fact, manufacturers are all jumping into it, making 'half-breed' BP BCDs for these divers. More than 80% of the backplate divers I've seen are not able to maintain trim, carry tons of rubbish on their D-rings. Some have so many D-rings and pouches attached, making the molly vest Navy Seals wear to war pale in comparison. What streamlining are we talking about?
To truly understand how backplate system works, one should study how and where the system comes about. There is no better way than to study the source.. DIR diving.
All the benefits of the bp stability is useless if one is still diving and hovering in a seahorse position. Weight distribution advantage is nulled with an overweighted diver, streamlining is not achieved with a poorly configured package.
Inherent reliability of such BCD are also gone as manufacturers make fashionable BP BCDs to cater to these 80% crowd, adding bells and whistles such as plastic 'quick release' buckles, pull dump valves, extra dump valves, silly paddings and over size wings with bungee cords (one size fits all wing). A totally opposite direction to the "less is more" concept of a true BP system.
Therefore, bp or not, which bp? There is no simple answer to this, one really need to do some serious homework and some face to face talk with the right person. I'm not suggesting you can't buy fanciful Bps, every diver is free to choose, buy one that you fancy, please go ahead. But without understanding the original BP concept, one will rarely enjoy the benefits. Remember, bp is part of a diving system, not just a stand alone miracle item.