264, your reasoning behind the 270WSM make good sense.
It is also true that if someone uses factory ammo & doesn't plan to reload they should get a 270. There are alot of great loads & some quick ones with good ballistics. For most folks, it will do what they want & then some.
Now, when it comes to loading both rounds to their max. potential the 264 pulls away & there is no way around it. For target shooting, due to the 260, 6.5X284 & to a much more limited degree the specialized use of the 6.5-300Wea. & .264WM in 1,000yd.
matches, we have alot of 6.5 match bullets. Because the 270 is pretty much a non-factor in comp., 270 match bullets exist, but the choice is very limited, nor does the BC's compare. These can also be used (in very rural places) for windy day, limited Varmit shooting,
the 6.5 would rule here.
This also brought along the A-Max, for the 264, that is. Hornady themselves say you can use it for Medium Game & it sure works for Deer/Antelope. Not the best for up close, but for someone who knows how to shoot a rib cage, no problem. BC is .550 for a 140gr.
6.5. Oh, and some may have forgotten about the new Swift Sc. & new Nosler Acc. bullets. These have a higher BC than the 270
130gr. bullets, the Swift is .571, combine this BC & the higher vel. of the 264 & the difference will be dramatic!!!
Also, new powders such as Retumbo & RL25 are helping rounds like the 264 more than they can help a std case. So, with a rifle like the new Sendero 26"(BTW, the vel. increase with these new powders is a little more than 60fpsin a 26", sorry), it will be no trick to get 3,300-3,350fps with a 130 & 3,200-3,250 with a 140, & the modest velocity over the 270 & the more dramatic BC increase
will give you a noticeably flatter traj. & it will be somewhat more than the 5" @ 500yd. figure mentioned.
Something that I have noticed for many years concerning this comparison is that with very rare exceptions those who use both rounds will tell you
the 264 is superior in ballistics. Those who say the 270 will run with the 264 with very rare exceptions only use the 270, & to me, that speaks
volumes!!!
More important than trajectory by far & not yet mentioned is the difference in wind drift & this difference is SUSTANTIAL. As someone said before, you can aim higher, but the more windage allowance you have, the harder it gets & this is the REAL challange.
The 270 is great in it's own right, but no need trying to say it will fly right with the 264 IF BOTH ARE LOADED TO THEIR POTENTIAL,
because it won't.