The reason I like the 270 better is pretty basic.
I compare apples to apples.
There is not an argument that the best of the .264" VLD Target Bullets have an advantage in their flight characteristics over about anything else short of a 408 Chytac and the 50 Browning target bullets.
However I don’t shoot targets for any reason other than to zero in my hunting rifles.

Hornady makes a hunting bullet in .277” that goes a bit over .500 BC. There are a FEW .264” bullets that top that number, but dang few and ALL of them are target bullets.

So for a dedicated paper punching rifle I am sure I would also go to the 6.5 in some configuration.

But that kind of shooting bores me.
I have nothing at all against those that love it, but I just don’t.

When it comes to HUNTING, the 270 has shown me that it lacks nothing within the range of body size animals I’d use it against and about any range up to about ½ mile.
And there are a lot of GOOD long range HUNTING 270 bullets to choose from.
And there is no argument that a bullet that shoots 8” flatter at let say, 500 yards is of NO advantage to one that shoots 5” lower unless you can hold the difference.

So if my 270 shoots a few inches lower at a given range than a 6.5, it makes no difference if I hold a few inches higher.

If you can’t hold the difference then you should not be shooting at all at an animal.

A slightly better BC holds it velocity a bit better than a slightly lower BC. That can help with group shooting. Animals (or men) don’t let you shoot groups. I have no need for that supposed advantage. However a bullet that acts like a hunting bullet on impact instead of a target bullet?
THAT is an advantage I can and do use.