It's true that's it's not as powerful -I really wish it had the same SoC as the Zero- it looks like it runs everything before PS1 just as good.
And besides, lets face it; the GCW0 was not running PS1 games well at all. Maybe a few of the earlier at simpler titles at close to full speed, but it struggled with the vast majority of the library.
True, there's some games it struggles with, especially if the game is one of the few on PS1 to render a true 60FPS on the original hardware (Tekken 3, for example). Most rendered 30FPS at most, despite what an emulator's FPS counter tells you. However, PCSX4ALL runs many 3D games on GCW Zero well, many full speed, some needing frameskip enabled. And there are improvements being made now behind-the-scenes to increase performance even further. Some of these depend on jz4770 (GCW Zero CPU) features, such as MXU SIMD rev2 instructions, which the RS-97 and Dingoo A320 lack. Happily, however, many of the improvements will apply to all MIPS architectures.