Nice little demo video that shows off the internal layout and economy advantages of tanks having a hybrid-electric drive. A development that has been WAY too long in coming. What they don't show, however, is one of the best advantages of HE drives – STEALTH!
If you don't have to have a noisy/hot engine running in order to be able to move and reposition short distances, the enemy is much less likely to realize you're there. Whereas a turbine-engine tank like the Abrams looks like a Roman Candle in the IR sights that even third world countries have now.