This is virtually the ONLY thing Snes9x has over ZSNES.
If any of you saying this knew what they were talking about, you'd be well aware that SNES9x is quite a bit more accurate than ZSNES is. FF5 title screen, Madara 2 intro, Earthworm Jim 2 audio, SimEarth worldmap, SNES Test Program - electronics test, PPU1/2 open bus support (if imperfect, missing $213f PPU2 open bus support), OAM interlace support, near perfect OAM size emulation, proper Mode7 EXTBG support, Mode7 direct color support, pseudo-hires emulation, Mode0-4+7 interlace support, the SPC700 emulation actually counts opcode cycles, DRAM refresh emulation, fully portable, non-x86 dependant source code which is easier to maintain, and this is all just off of the
top of my head. I won't even discuss the unreleased v1.44 branches' new features.
But yeah, a fake trick involving extra precision with Mode7 calculations is the only thing it has over ZSNES.