I believe the bullet themselves to be used come into play a bit on this. In
@RPRNY 's example of the two .30 cases with a 180, the longer boattail certainly supports this as it is the nature of the beast. However, if we instead used a flatbase 180 gr bullet, the actual trade-off if loaded properly should be less noticeable. That is not to say that a .7-08 can compete with a .280 in terms of overall heavy for caliber performance as the case capacity in general is just not there. However, the lack of velocity with a flat based design will not be adding that much to tip the scales.
In today's world, a flat based bullet is STILL plenty capable of many field uses. For many marketing schemes however, the public is taught to believe that you MUST be able to knock a squirrel off the back of the elk you are glassing 850yds away or else you're using the wrong equipment. For hunting applications, the difference is beyond moot.
On the other hand, if one is determined to shoot past 500 yards and desires the better b.c. of longer bullets for wind resistance and drop, then of course, everything from actual velocity, trued b.c.s and neck tension becomes more apparent the further you are from the target. Even so, the short necked .243 & .243 AI are still loading the LONG heavies with enough powder to reach a 1000 yd target with ease.
At the end of the day, when firearm technology was much less advanced, such concepts were much more important than they are now. With such advances in both the bullet and propellant industries I believe the bigger factors now come down to sheer case capacity. The huge 26 nosler, when loaded with the same bullets, will only run out of steam somewhere between 100-200 yds after the .264 win Mag. For most people, the difference between 1750yds and 1850 is so negligible it's a non issue. The same comparison on similar cases with the slightest overall difference in actual neck length, and the subsequent difference in case capacity based solely on neck capacity, is equally subjective to the individual purposes. I personally view the actual case performance debate placed upon neck length as mix of the need to debate SOMETHING and an excuse to BLAME equipment for shooter error. If you can hit a target 1000 yds away with an 06, the only thing stopping you from doing so with a .308 is yourself and lack of practice.
The best example I can think of to illustrate this, is the 06 based 7 & 6.5mm cartridges vs the .284 win and its 6.5 spawn. The .280 neck is .056" longer than the neck of the Winchester cartridge but the only performance differences can be chalked up to the length of action tolerances to chambering long bullets and chamber tolerances for same said long bullets. These differences can, of course, be negated with properly constructed firearms, made with allowances for longer C.O.A.L.
