Off-course, if majority of your time is spent compiling gigantic C++ codebases, more power to you for using VIM. CPU load in code compilation hasn't been the bottleneck I ever faced and I think this applies to most folks. Plus CLion doesn't just arbitrarily start consuming CPU, if it is not doing indexing(and VIM simply can't do the kind of indexing that CLion does), it doesn't consume much CPU. In the idle state, it consumes very little CPU.
Then again, some seconds of CPU might be a good tradeoff against productivity in some scenarios.
I don't spend the majority of my time compiling (a decent chunk though!), but then again, I also don't spend a large part of my time doing the complex refactorings that an IDE would make much easier. I don't think either vim or clion has dramatic advantages over the other.
Then again, some seconds of CPU might be a good tradeoff against productivity in some scenarios.