Wide baffle speakers are better than narrow

In my jbl bibles it shows how to construct and brace 4x8 sheets of plywood beside the speakers for behind screen. I would imagine it has to do some with efficiency . And no in wall speakers  arent a go to. Unless you like the sound of plastic and drywall with zero placement adjustability.  

I imagine using a bigger baffle puts forward the true image more as opposed to hearing the room youre in. I’ve never been in love with the narrow speakers . That being said i love the sound of L7 so much i have two sets . And L5 . But my current rig 4430 w a 2441 and a 2405 on top is girthy  and feel like my retirement speakers, they are very reference like. Nothing i see these days interests me.