Performance issues of emacs (made much worse by many layers of plugins), combined with vim’s counterintuitive bimodality, originally meant to compensate for slow terminals? Thanks but no thanks; for me, Spacemacs took the worst from two editors. I love the eye candy, though (when it works); however, it’s not enough to compensate said curious choice.
I rarely see any performance issues, even when running spacemacs over ssh. The only issue I have is start-up time and there are ways to speed that up.
I run it as a daemon that is managed by systemd. The startup time is the time it takes for my window manager to create a new window.