Get 2x msaa on watch dogs (or any game that uses txaa) and then force FXAA on it via either sweetfx, or nividia inspector. The combination of 2x MSAA and fxaa won't be even a fraction of the quality of TXAA 2x. Same goes for 4x MSAA + fxaa vs TXAA 4x. Txaa almost eliminates temporal aliasing, whereas fxaa and msaa in direct x 11 barely touch it. The shaders that txaa uses are very different, and the whole thing is designed to work as a multi-pass system. It's like saying that HBAO+ and SSAO are the same because they are both technically ambient occlusion. Whereas they are very different and "think" in very different ways. For me the look of what TXAA achieves is closer to sparse grid supersampling 8x in direct x 9. Better than that even. MSAA and fxaa do complement eachother, however they are WAY different to TXAA in antialiasing functionality, have a look at the shaders if they ever release the code, i am willing to bet there is very little in common with smaa/fxaa for the post processing part of TXAA.