[Question] what is better for performance , BSP or Static Mesh?

The current build we are working on Uses BSP for most for each Map and then Static Meshes in certain places. Would it improve performance if the BSP surfaces where converted to Static Meshes?

Also when using BSP is it better to use one large BSP surface or split it up into smaller chunks?

static meshes are more efficient for performance.

https://rocket.unrealengine.com/docs/ue4/INT/Resources/ContentExamples/BSP/index.html