Reef Builder main components are Carbonate/Bicarbonate, Chloride and Sulfide salts, with mainly Sodium as the counter ion. The high percentage of Carbonate/Bicarbonate has to affect pH by definition as it is a buffer, but is probably at a ratio that will stabalize things around 8.1-8.2.
Advantage Calcium contains Sodium, Magnesium, Calcium, Strontium, and Potassium salts, with mainly Chloride as the counter ion. None of these are very good buffers, so there will be minimal effect on pH with this. No CaOH here, as with Kalk.
Reef Buffer, from what I gather from Seachem, is similar to Reef Builder, but loaded with NaBorate to effectively raise and/or stabalize tank pH around 8.3. It is meant to be used with Reef Builder to raise pH.
Chiton