Weight and current

A question that is interesting me:
What will be the current draw different If I have exactly the same electronics (ESC + Motor) on Truggy and Buggy? (Both are set up for the same speed)

In other words, if the Buggy is 25% lighter then the Truggy should I expect 25% less current consumption then the Truggy? If so, If the Truggy is using 5000mAh 4S battery, can the buggy use 25% lighter battarry (3750mAh) and expect same run time and performance as the Truggy?