When working in a higher-level language, it's easy to forget that a lot of the performance disadvantage comes from using data types that are distanced from the hardware, require unboxing, RTTI, etc. Not only do those conveniences eat up CPU, they also eat up memory, which compounds the problem by forcing the data to live outside of cache, regardless of what optimizations the language implementation has.

Hence, I really appreciate it when a language offers some way to drop down to byte-level constructs and build space-efficient implementations where they're necessary. Improvements in memory compactness can often save you the effort of dropping all the way down to C.