Hi.

Carrying a load on a vehicle takes some horsepower; pulling it shows another figure.

Is there an approximate percentage that tells difference ?   Like towing 50 Kg needs 40% less horsepower than carrying 50Kg ?

-Images borrowed from the net-

There's no intrinsic reason for a difference. Possible slight variation might be more rolling friction on towing, because more wheels are spinning. And the towing example shown would probably encounter more wind resistance. So towing, on the face of those examples, would need more power, but not because of towing vs. carrying. 

3 hours ago, Externet said:

Is there an approximate percentage that tells difference ?

No
Except, I guess, saying "50%" can only be wrong by +/- 50%