It's more compelling because a number of research groups and companies are investing in designing and releasing hardware based on it. It has mindshare in the space that Power does not and is not likely to have.
Just opening the ISA doesn't mean that new players can start spitting out processors based on it tomorrow or even next year. And why would they want to? Power was never in remotely the same position that x86 is/was re: binary compatibility so being able to say 'Power compatible' doesn't carry much weight. An ISA which has been a minority player but around for a long time is more likely a liability than an asset.
For RISC-V to be a more compelling option than Power, it would need to be an option first, but if I need to buy a CPU today, I can't buy a RISC-V one.
I can, however, buy a wide range of PowerPC CPUs, for a wide range of applications. From embedded applications, like routers, to laptops, desktops, workstations, high-end servers, up to super-computer class CPUs.
Just opening the ISA doesn't mean that new players can start spitting out processors based on it tomorrow or even next year. And why would they want to? Power was never in remotely the same position that x86 is/was re: binary compatibility so being able to say 'Power compatible' doesn't carry much weight. An ISA which has been a minority player but around for a long time is more likely a liability than an asset.