Adobe scratch disk- Get a larger SSD or adding a dedicated SSD?

Hi, my C: drive is a 180GB Intel 330 series SSD which only has about 47G free space. I am thinking to add a scratch disc for Adobe premier.

But I have 2nd thought, why not upgrade the 180GB to 256GB (Samsung 860 series) then use the same drive as scratch disc. That way I can reuse the 180GB drive in my wife PC. We will both be happy.

pros and cons?