Looking over the patch notes for tspy, looks like they have some cool stuff that some people would like better. A few things I noted would be cool if HC implemented and some might get a HC version. Based on notes, I think there's more development from HC, but Thunderspy has some more flashy stuff.
For myself, I wouldn't be able to play two similar servers, so I'm not going to check it out further, but I think others may find it interesting.