The German occupation was significantly more brutal, considering Germany suffered some million or so civilian casualties from all military actions (including those of the western allies,) compared to the 8-12 million inflicted in the Soviet Union.

The Russian occupation is, I feel, often played up due to the political concerns of the time. Yes, there are accounts of rapes by Russian soldiers, but there are also accounts of Soviet troops handing out food to orphans.

The thing is, the Russian plan wasn't to murder 2/3 of the German population. The Nazi plan for Russia was to do just that. The Soviet high command issued orders against rape and murder, although depending on commander this was sometimes not enforced (as in all the allied armies.) It may have been more of a problem for Soviet forces, but then, virtually every Russian soldier would have personally known somebody who had been killed by the Germans.

The difficulty in finding good sources on this issue is that it has become highly politicized. It's difficult to find a middle ground between "the Russians were barbecuing babies in the street" and "glorious Soviet soldiers were all angels and did nothing but help the German civilians." The truth is probably somewhere inbetween.

However, I do firmly believe that the "Stalin's army of rapists" line can be firmly dismissed as Cold War era propaganda. This is not to say that the Soviet occupation was not brutal and that rape did not happen, but the scale which is hinted at (but seldom given a hard number,) in English sources is probably exaggerated. Sadly, it would be difficult to exaggerate the horror of the holocaust in Russia.