Yes If using single EOG then EOG car has to shunted at the back of the train every time the train runs in UP/DN direction.
EOG has 2 Diesel Alternators(DA) whereas LSLRD has single underslung DA with the converting capacity.
So, if using a single EOG in Rajdhani/Shatabdi/Duronto/AC Exp then it will reduce the cost(Electricity per unit) drastically.
If taking LSLRD, then it can...
more... be used on either end of Exp trains.
IR says LSLRD will be useful as it will provide seats for Divyaang. For this point, I want to say, provide full LHB GS coach instead of LSLRD and use single EOG which is enough(Tested by RDSO and IR) for power supply.