That question is best answered by spending some time perusing the Internet. There is a TON of information about this out there for the asking.
The short answer is that RISC means an instruction set that has a relatively small handful of simple instructions that, as a result, can be run at much higher speed. CISC is the opposite in that you have a relatively large number of complex instructions that, individually, get a lot done. But, as a result, you can't run the processor as fast.
With RISC the same program usually requires a lot more instructions to accomplish the same thing, but you can execute most instructions per second. There's no fundamental reason why a program running on a RISC machine will finished sooner or later than the same program running on a CISC machine. Some will run faster, some will run slower.
With the current technologies, RISC has the preponderance of advantages, but that wasn't always the case and it may not be the case twenty years from now.
With that level of understanding, do think the Hack is RISC or CISC?