Is there a benefit for using this versus Picodrive?
That depends. For SG1000, Game Gear and Master System you have the benefit of full screen emulation and correct colour rendering and optional FM sound on some Master System games. For MegaDrive/Genesis you have better sound emulation.
Overall Genesis is generally a more accurate emulator so will probably have less glitches than Picodrive.
However Picodrive is optimised for speed so is currently better for Virtual racing and fmv sequences in Mega CD games.
I am in touch with the Genesis Plus GX developer ekeeke who has suggested a way of improving MegaCD performance so hopefully this can be improved further.