I guess much is taken for granted. It is good to be patient. I just read about horizontal dispersion. Makes sense. Now what? I was just looking at the Genz Benz NEOX-212T 600W 2x12 Bass Cabinet. This is verticale mounted and designed that way. Are we saying here that manufacturers are making a product with inherent flaws just because? While others like Genz Benz are doing some things right?
Genz Benz makes a couple VERY nice 410's.
Again, it is kind of like talking about aerodynamics in cars. There really is only one absolutely best shape for a car, but varying that a bit makes things more interesting and results in only a very slight performance issue, in the thread's case, a bit less upper mid dispersion.
I have 'vertical' 212's and also various 410's. Yes, there is a slight difference in disperson in the upper mids area. However, the vast majority of 410's will bury the vast majority of 212's in absolute volume and projection. So, pick your poison.
That being said, that Genz 212 is a nice one... very tight, grindy, bright and punchy. I prefer the Bergantino AE212. Of course, 12's still beam a bit in the upper mids, so if you really want to 'drink the Kool-aid', you should look for a vertical oriented 212 with a mid driver

However, those boxes have their own inherent tone that you might or might not like.
I recently purchased a wonderful sounding Audiokinesis Thunder Child 112 that takes another approach to the dispersion issue in the upper mids... using a relatively low crossed over PA type horn to the top end of the bass guitar's sound.
All nice stuff, but I would NEVER pick a cab based on slight dispersion improvement in a relatively narrow range of the bass guitar if I didn't dig the tone.
IMO and again, a ton of IME on this one!