There are many variations of formulations of PBS. The main distinction is whether or not they have calcium and magnesium. I would assume that either of your protocol versions will be fine. If it matters to you, I happen to use the dibasic versiion d sodium phosphate.o
You have to use Na2HPO4 and KH2PO4. Basically u have to use a dibasic and a mono basic salt for this buffer to set pH unlike the tris buffers where u use HCL or NaOH to adjust pH. So u have the sodium dibasic (more basic) and the potassium mono basic (more acidic) in this recipe. Hope this answers it.