besides jemalloc also being used by other columnar databases it has a lot of control and telemetry built in. I don't closely follow tcmalloc but I'm not sure it focuses on large objects and fragmentation over months/years.

TCMalloc has an absurd amount of bookkeeping and stats, but you have to understand the implementation deeply to make sense of the stats. https://github.com/google/tcmalloc/blob/master/docs/stats.md