Physics body made of multiple simple polygons or just one complex polygen, P2 performance

[megabyterain]

I'm making a game with a lot of asteroids. I noticed that my fps drops the more asteroids I add when running on the 2015 i7 Macbook Pro. That probably means that on less powerful laptops will lag a lot? My asteroids are similar to the ones in the game Asteroids, however I wanted them to have a somewhat realistic collision body shape that represented the sprite shape. On the Phaser p2 examples I noticed that the json for physics bodies' shapes were broken into smaller shapes
 like this

{
[1,2 , 3,4 , 5,6], //pretend that this is a triangle
[7,8 , 9,10 , 11,12], //pretend this makes another triangle
[13,14 , 15,16 , 17,18] //pretend this makes another triangle
}
//pretend if you put all of the those shapes together it would make another shape

as opposed to just having it as one complex shape like

{
[1,2 , 3,4 , 5,6 , 7,8 , 9,10 , 11,12 , 13,14 , 15,16 , 17,18] //pretend this makes a shape
}

Which is better for performance?

Also I want to have maybe around 200 asteroids in my game at a time, not to mention some other bodies as well. Should I reduce the amount of vertices of the asteroid's collision bodies? Would setting it to be a circle be less power demanding? The game works fine on my desktop, but that has a gtx 970 and I doubt most people who play my game will have that sort of power.