oh hey, I'm the developer of SpiceyPy. IIRC jplephem implements their own parsing of spk files and isn't a full implementation of the SPICE API. SpiceyPy simply wraps SPICE (via CSPICE).
This is consistent with what I know. I did not need the full API for my use case, just access to planet positions across times in the next few decades.
It is Dmitry Savransky who recommended your package, btw.
