bZSNES emulates almost all of the major features of ZSNES:

    VRAM can be written at any time, even while screen is rendering
    OAM and CGRAM can also be written at any time
    DSP echo buffer writes do not interfere with APURAM
    DRAM does not need to be periodically refreshed
    H/DMA synchronization does not steal CPU time
    auto joypad polling results can be read immediately
    CPU multiplication and division register results can be read immediately
    mid-scanline writes to PPU registers do not interfere with video output
    PPU background and sprite layers can be individually toggled on and off
    DSP voice channels can be individually toggled on and off
    CPU speed can be adjusted from its official frequency
    ... and more!