The memory management can be quite suboptimal. I wrote the same program in both at one point (an experimental language transpiler) and the Crystal version would

The memory management can be quite suboptimal. I wrote the same program in both at one point (an experimental language transpiler) and the Crystal version would spiral up into the 10s of GB when converting a very simple file while the C++ version wouldn't even hit 1 GB. No doubt there was something I could have done to coax it into behaving, but in C++ that was unnecessary. RAII and ordinary standard library containers were enough to make it work. This was a while ago, so perhaps things have improved.