the standard use of hiem joints on those "bling" bars, are to have an adjustable preload on the suspention. not all cars are made EXACTLY the same.
I wouldn't say that those will not help. It will, but the way strut tower bars are to stiffen.
(you all probably know this, but for those that don't and for those who can correct me ) Imagine the x-member and the strut towers as a incomplete rectangle. Now when you load one side (as in cornering) it will cause it to warp more into a trapazoid. Now a bar will complete the "rectangle." The "bling" bar will help the towers from changing inward and outward, but will cause it to change to a rombus in cornering. Now a "solid" will keep it more of a regtangle and keep it camber, toe-in and other suspension settings stable and more static as far as the frame is concerned in cornering.
(go ahead and correct me if I'm wrong)