Sega only put it there to pass FCC Regulations.
Just like them metal plates and clips for both CD and 32X. Just for FCC regulations. Everyone knows that.
Oh, and if your referring to the picture quality over the Genesis only, that's because the 32X takes the clean RGB signals and NTSC/PAL encodes it by itself, with a slightly better encoder.
Once again nothing to do with the ferrite bead, but more of the encoding chips involved.