Often it serves you better to cripple your enemy's towers
and structures rather than destroying them outright.
If you destroy an energy tower, for example, he can simply
place it elsewhere, which forces you to chase down the new one.
On the other hand, if you leave the tower crippled and burning,
its efficiency will be severely impaired. He'll have to come
back and destroy it himself in order to place a new one just
the kind of time-wasting action that will help you win the scenario.