Reactive fighting is just that, reactive.
I am not a big fan for many reasons but the most obvious is that it makes your body react to the situation based on how it is drilled, in other words:
Training to defend a punch coming at you WHEN you want it, to WHERE you want it and HOW you wanted will do nothing for you when Billy-Bob tries to tee of your head with 5 years of pro boxing experience AND when you didn't even know you were in a fight yet !
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !