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NPN vs PNP, a fundamental or just a mental difference

Like many here, I were in need of a bit of amplification of a weak signal. This signal had "low impedance", I suppose. The supplied circuit diagram shows two different ways of meeting my need.

The left circuit uses a NPN transistor. The right hand circuit uses a PNP transistor. I chose the one with PNP. Quite "arbitrarily". The BP103B is also known as FA300.