Who wins?
"ok" vs "talk soon!"
"talk soon!" wins 85% to 15%. 24 more put them in the same row. From Ways to Say Goodbye in a Text Tier List. Pick a side.
TylerWas_Here on "ok": ok with no punctuation is chilly
SoggyGecko16 on "talk soon!": the polite way to end it without making plans
Ways to Say Goodbye in a Text Tier List: the full ranking