In that case yes, it's the sensor. I know sharpening in Adobe Photoshop, but this is not something Photoshop can replicate. I guess you will need to really use both to understand. The lines just can't be as fine using Photoshop and the effects are significantly different. I have been using Photoshop for 550D for quite a while, so I would have some understanding regarding that.
I see. Well I've edited a few thousand images done with my 50D. It had digic 4 processing, was an aps-c, but was "only" 15MP, etc. I never noticed the outlining that you're talking about, in it (nor have I noticed outlining from full size pictures I've seen from cameras like the 7D, on the web). The only real difference I see between the detail via my old 50D's RAW files when viewed at 100%, and those from the 6D (besides the different amounts and types of noise at different levels of ISO)...is that when the luminance noise (the "grain") is at a similar level (say if the 50D is at ISO 500 and the 6D is at ISO 1250 to 1600)...then the 6D's grain structure is a bit larger. It's not quite like the difference going from the 6D to the 5D3 or 1DX. Their files show a grain structure that is more than twice as large as that from the 6D (relative to the size of the pixels). The 50D's grain is well over half the size of that of the 6D, but it's noticeably smaller. Again, this is viewed at 100%, it's not relative to the total size of the image, since the 6D's image has more pixels. And certainly the color noise from the 50D was always more of a problem than the grain...but then both got to terrible levels before I wanted them to!
Another improvement is a greater dynamic range (even at low ISO), apparently the 50D's was not all that good, at least compared to the 6D. The 6D in turn does not have the highest DR at low ISO, either, especially compared to Nikon.
By contrast, the old Rebel Xsi 12MP camera I used to own, did indeed look less detailed when viewing a RAW file at 100% (and it had vastly less DR than the 50D..and a lot more noise). It kind of looked like aliasing problems to me. That was "digic 3 processing" though. I assume the sensor that is in the current "Rebel T3" camera, is closely related to that sensor. I guess they wanted to make sure the IQ from the current "T3" camera, matched the feel of its body and grip...CHEAP and compromised.