i'm no expert but I can't see a massive quality difference between the two. I am a massive fan of ffdshow for things like upscaling and deinterlacing and the way you can fiddle with the settings to optimise the picture, but for h.264 its best to leave the stream unaltered as much as possible and so it loses the advantage.
These days things have got a bit more complicated as most modern cards will offload the h.264 processing to your gpu with very good quality.
What I suggest is that you use MPC-HC as it will handle DXVA acceleration where possible, plus it has good h.264 software support via libavcodec (came codec as ffdshow anyway) to fall back on. Its also a very clean solution as no codecs need to be registered with windows at all. Its also free which coreavc is not.
Above all avoid codec packs.