It's the same picture, but the Guardian one is compressed horizontally to fit, the Post one is not. It's obvious that whoever made that slide used a larger image but positioned it so that only part of it was shown. Post opened it with PowerPoint and it rendered correctly while Guardian opened it with OpenOffice which mangled it (look at the arrows and circles too). Most likely it's the Guardian that redacted the name of the two programs for whatever reason (they said they are curating the leaks to not cause unnecessary damage and not just dumping everything).

It isn't, in some way. PowerPoint let's you "mask" images. That is, bundle the entire image in the PPT but crop and zoom it. Of course, whoever did that slide zoomed into the US. It isn't a purpose-made image, but rather, one illustrating how traffic flows to and from the U.S.

Fits perfectly with the "different software" idea. Pages, Google Docs, OpenOffice and even different versions of Office produce different results with the same PowerPoint.

That would be congruent with the dropshadow displaying on the "You Should Use Both" text in the (presumably) PowerPoint-rendered one that is masked correctly. It doesn't seem to appear in the other.

EDIT: Also, on the US-zoomed/masked one, it makes the ellipses line up correctly with all the cable landings at the coastlines. I'm now sold that these differences are just PowerPoint-specific renderings.

These come from the NSA originally - so it's probably SOP to make slight changes to every page of every document each time it is released to someone, so that they can track the exact source and path of any leaks.

Wouldn't that suggest two leaks of the same document (one to WaPo, one to the Guardian)? I don't believe that is the case here.

I don't doubt they version things like this, but I do doubt the watermark is easily found. A bit here, a bit there and you can bury a lot of info in a graphic with no one the wiser.

Or someone just decided that a US map would look better for the other briefing.

On the US-map one, the ellipses line up correctly with the cable landings, and the PRISM-partner logos are over the US, not floating in the ocean. Also, the arrowheads on the cable-bundle ellipses aren't all distorted, and the drop shadow on the "You Should Use Both" text displays correctly.

I'm marking this one down to PowerPoint-specific rendering (vs, say, OpenOffice).