Is there a difference in the energy produced from the hydrolysis of GTP and ATP?
As @WYSIWYG said in comments, there is no effect of change in nitrogenous base on the third phosphate. Why? Simple, they are too far to directly influence each other's stability. See the diagram (of ATP) below from wikipedia:



and of GTP from here:



What one can clearly interpret from these diagrams is that there would be no effect on the energy released by hydrolysis of the third phosphate by the nitogenous base present. It will remain -30.5 kJ/mol(1) in both cases.