User Info: Bristow84. No ending is considered truly Canon but based on what it shows the 360 version is the most Canon.

Are there two versions of Splinter Cell Double Agent?

There are two separate versions of Double Agent. One version was made by Ubisoft Milan and Ubisoft Shanghai, developers of Tom Clancy's Splinter Cell: Pandora Tomorrow and was released on the Xbox 360, Microsoft Windows, and PlayStation 3.

How hard is Splinter Cell Double Agent?

In my experience, Double Agent is the most difficult game in the series, because the game engine is buggy. I also found the level design frustrating. Conviction is the 5th game in the series and plays very differently from the previous iterations (Double Agent is the 4th).