One is in the corner flush while the other has wall only on one side (no chance of getting a wall there and false corner likely will look bad).
I suspect your main problem with imaging is a result of the room asymmetry noted in the quote.
Room treatment may help, as may experimenting with placement of the speakers or other objects in the room. Even something as simple as a coffee table in between the speakers and the listener can screw up imaging. Experimenting with the toe-in of the speakers or listening chair position may also help.
Our brain localizes sound objects in space by analyzing the differences in sound between the left and right ears. Transient arrival time is involved, as well as the relative loss of high frequency response to the ear in the "shadow", and below about 1,500 Hz, the phase differential between the left and right ears is noticeable.
If the fundamentals of speaker placement and room acoustics are not basically correct, it is very tough to make up that distance with equipment changes or tweaks.