While the Wii version may be a weaker game than it's next gen counterparts, it's still a fun game, minus multiplayer.
Sam Fisher's mission is his most dangerous yet in Double Agent, he has to infiltrate a terrorist organization in search of Red Mercury, but this is a review, not a plot outline, so I shall keep the plot details minimal, but basically Sam must go undercover and perform certain acts that will please one side of the law, whilst aggrovating the other. This is the new trust system. While doing certain acts like not killing any innocents may raise your trust with the NSA, will not affect your trust with the JBA, some tasks will require intricate balancing between the two organizations.
[WII] The Wii version of Double Agent looks a little rough. Textures are muddy and rough around the edges, most characters don't move there mouths when they talk and some other graphical blemishes diminish the environment.
[360] The 360 version looks almost identical to the Xbox version of Chaos Theory, with some next gen improvements. The animations are all the same, but Double Agents locations are alot more stunning, for example, when your falling through the sky and must activate the parachute at the right moment, the motion blur etc. really looks fantastic.
The sound in both versions is mostly the same, though the voice acting seems a little more enthusiastic on the 360 version.
There are two versions of Double Agent, version one and two, they feature different missions and a partly different story. Version one is the 360, PS3 and PC version. It features the very basic Double Agent plot, with some next gen enhancements and mini-games here or there. Version two is for last gen consoles and the Wii. This features a slightly different story, but with more detail than version two, yet it misses some of version one's features.
[360] The 360 version features the strongest online multiplayer of the whole bunch. Spies versus Upsilon delivers heart stopping excitement and brilliant thrills.
[WII] While some versions of Double Agent feature either Spies versus Spies multiplayer, or no online multiplayer, just offline, the Wii version goes one step further and features no mulitplayer whatsoever. This really hinders the replay value.
Of the two versions, the obvious choice is the 360 version, but if you only own a Wii, then there is nothing wrong with settling for a watered down version of the game. You just get a little less for your money.