What advantage does it have?

[Zundfolge]

I have read articles and spoke with people that claim the 45 acp has a better inherent accuray than the 40.

I hear that a lot too but I think that has more to do with launching platform then the bullets themselves.

There's a LOT of 6" 1911s and tricked out raceguns shooting .45 and I'd say most of the .40 guns out there are Glocks and other "duty weapons" which are clearly not as accurate as competition guns.

Also, I've found that 180gr .40 just doesn't shoot as well as the lighter ones ... and since 180gr is the most common weight for .40 (because the 10mm was built around a 180gr bullet, and the .40 is the stepchild of the 10mm) I think most people's experience with .40 is with 180gr bullets.

 

[Lancel]

Here's an interesting statement in an FBI study on the 9mm, 10mm and .45 ACP:

As an additional consideration, the 10mm was by far the most accurate round tested, consistently providing one hole 10 shot groups at 25 yards of less than an inch (0.77" average) with both handloaded and factory ammunition built to FBI specifications. By contrast, the 9mm averaged 2.3" and the .45 averaged 2".

The 1989 report is here.

For most of us there are too many variables to make an easy comparison between calibers.
For me, the real (and more relevant) question is the most accurate bullet / load in a particular individual firearm.

Larry