It depends. It depends if your application is 32-bit or 64-bit.
PGNP OLEDB provider is an In-Proc COM server. In-Proc COM server is essentially a DLL. DLL loads into the process space of an application (EXE).
Windows 64-bit allows to run 32-bit applications utilizing WOW64 subsystem.
Windows 64-bit only allows to load 32-bit DLL by 32-bit EXE and 64-bit DLL by 64-bit EXE.
If you are planning to use PGNP from 32-bit application then you need PGNP 32-bit.
If you are planning to use PGNP from 64-bit application then you need PGNP 64-bit.
If you are running 32-bit and 64-bit applications under Windows 64 then you need both 32-bit and 64-bit providers.