Stationary directional light performance cost on static objects

HI, I have done some testing on foliages with static and stationary directional light and i notice the lighting on stationary lights are considerably better on stationary. Below screenshots for comparison. The Direct light doesnt seem to exist anymore on the leaves after light baking on static directional light.

Apologies for the noob question but i would like to check what is the performance cost on using stationary directional light if my scene only has static objects. Is there any way to quantify the cost? I am trying to create a scene for VR so trying to save as many frame rates as possible.