how heavy are impact events really ? (compared to onBeginContact)

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game.physics.p2.setImpactEvents(true);

 player.body.createGroupCallback(enemyGroundCG, playerCollision, this);

this is what i use most of the time but i've heard that using

a onBeginContact event is not that much expensive..

 

 

to gain some FPS - is it really useful to change the impact handling?  does this really matter?

 

 

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so i gave it a try..  i disabled impact events and changed everything to onBeginContact events..   well .. it looks like the bottleneck in my game is somewhereelse..  i didn't notice a thing !

 

 

 

maybe the difference just doesn't matter if you only have 4 types of collision groups  and you do the individual checking with some "if statements" like (if body2.sprite.name === 'tux' do this elseif body2.sprite.name === cow do that)