I'll say it once again, slooooooowly, so you might understand:
1) I am not directly comparing the current legal situation/status of Knox and DSK.
2) It would, in any case, be impossible to directly compare their situations until any final convictions or acquittals, owing to the different justice systems.
3) Although, having said that, both are currently unconvicted of any criminal offence: Knox has been found guilty in a first trial, and DSK has been indicted by a Grand Jury, but neither stands convicted of any crime as of right now. You don't seem to know (or understand) this, but both Knox and DSK are currently presumed innocent in law in their respective countries.
4) Now for the important part: what I am comparing is the reason why both of them were incarcerated (at least, up until a few minutes ago in the case of DSK). Both of them were remanded into custody for reasons that were entirely unrelated to any criminal conviction or associated sentence. Both are (were) incarcerated because of flight risk before the culmination of the judicial process, and/or a risk of re-offending during the same period.