I would not call it "very" different, but I see what you are saying… there is a difference.
Apparently, Adobe's approximation of Canon's Landscape mode is just that, an approximation. My suspicion is that ACR default Blacks (+5) is too strong in comparison to DPP. Perhaps by moving the slider to +2 or +3 would generate a much closer rendering. I could not confirm that in LR, as jpegs have zero as a default for Blacks, i.e., I could not lower the black point of a jpeg to prove my theory.
However, I did the following adjustments in LR to the jpeg ACR2:
- Fill Light +20
- Blacks +5
- Brightness +15
- Contrast −20
Taking into account that I am doing those adjustments to a jpeg, I believe the rendering is quite close, if not identical to the camera's jpeg: