MAME's DRC is caching, meaning the translation pass to x86/x64 binary code runs once per instance of emulated (MIPS/PowerPC/SH-2) code and you therefore get the run-time performance of a static recompiler without all of the problems. (And since it's dynamic, it can handle the self-modifying code that occurs somewhat frequently in e.g. ST-V games programmed by Success).
Also, it handles the complete instruction set of each emulated processor. The "dictionary" is unabridged.
And of course none of this is a new idea - the first non-commercial emulator with a DRC was PSEmuPro back in like 1998.