Unity sprite packer VS texture packer

Hello,
I have tested both of them and found that texture packer reduces sprite vertices count (significantly*) , but i have a question that might be stupid ( i want to be sure ): when i use texture packer i have to slice the atlas into single sprites. does i have to pack all the sliced sprites again using unity packer????

* I used 2 sprites and here is the results:
1- unpacked: 46 vertices
2- unity packer: 46 vertices (no difference)
3- texture packer : 9 vertices