In my simplistic mind. Just an observer and crypto-fan 
With NEM:
Account [ A ] uses "Delegated Harvesting" to give Account [ B ] the "importance" of Account [ A ]. When Harvest a block Account [ A ] receives the amount.
With NXT:
Account [ A ] uses "Leased Forging" to give Account [ B ] the "importance" of Account [ A ]. When Harvest a block Account [ B ] receives the amount.
With NEM:
Account [ A ] uses "Delegated Harvesting" to give Account [ B ] the "importance" of Account [ A ]. When Harvest a block Account [ A ] receives the amount.
With NXT:
Account [ A ] uses "Leased Forging" to give Account [ B ] the "importance" of Account [ A ]. When Harvest a block Account [ B ] receives the amount.
and there is small difference when it comes to "stopping"