Forest pack and nanite - performance impact

Thx for your comment. So there are no differences between import forest pack models/ use same ones in foliage regarding shading and lighting alright?
I mean, somehow imported forest pack costs more than foliage?
I´m asking because someone at my job is saying it costs more to render than other methods, but in my tests, it won´t happen. I´m a beginner and want a pro answer to show them.
Here are a few print screens I took (I hope it makes sense).

Left forest pack right Foliage

Thx a lot!