Pi hardware supports OMX and MMAL decoders. MMAL should give best results, but requires more processing grunt. At some point the default in Kodi was changed to MMAL, so I have a hunch the difference between installing 7.95.3 and later releases is that the older install has OMX as the default and this preference is retained through upgrades. Later installs (dictated by hardware support) default to MMAL.
Pi v1 hardware probably doesn't work great with MMAL due to the higher overheads whereas the 3B+ will be fine with them. You can change the decoder to experiment in Kodi player settings (needs advanced or expert mode).