Couldn't possibly disagree more

.
It's actually the opposite of this. The wider the dispersion, the worse the imaging will be. If you want super tight imaging, the last thing you want is a super wide dispersion speaker. It will certainly be more stable and throw a wider soundstage, but will be less clear and more diffuse sounding due to a lower percentage of direct sound at the ears. If you want a super good center image, you want a very narrow dispersion speaker. The LRS is actually a pretty good suggestion for imaging alone, though it has some pretty horrible flaws outside of that.
That said, wider dispersion speakers are easier to get a center image with, so may be contributing to what you're hearing with your LS50. Narrow dispersion speakers can be difficult to get a center image with, but when properly dialed in they'll image much better than a wider dispersion speaker ever will. Of course, the narrow dispersion speaker will never envelop as well as the wider dispersion speaker, nor will it throw as wide a soundstage. As with all things, there are pros and cons to both styles. My Revels are my worst imaging speakers by far, but they're also my most enveloping speakers. Overall they're excellent.
Also, your Revels and BMRs measure better on and off axis, so not exactly a fair comparison. To truly compare, you need a narrow dispersion speaker that measures as well as your wide dispersion speakers. Of course, the BMRs are actually kinda unique, in that they have very wide horizontal dispersion but very narrow vertical dispersion, which may actually be a good thing(more research needed imo).
I posted this before, but generally speaking, and all other factors held constant(they never are

):
Narrower dispersion will image tighter and more clearly
Wider dispersion will throw a wider soundstage
Wider dispersion will be easier to get center image
Wider dispersion will have a more stable center image(unless extreme toe-in is used with the narrow dispersion speaker)
Speakers with smoother off axis response will image more clearly, especially in more reflective rooms
Speakers with a tighter driver grouping(like the Q150) will throw a tighter image than big towers who's drivers are far apart
Speakers with symmetrical driver layouts will throw a tighter image
The best imaging I've ever heard by far (and it was under blind conditions) was the Danley SH50, a very narrow (50 x 50) point source loudspeaker.