Yeah actually you're right. Did some testing last night and yes with vsync off you get slightly better frame-rate and therefore latency due to frame-variances when you get frames that complete faster.
Basically Vsync means frames will never complete in less than (1000 / max frame rate) milliseconds. Sometimes they do, and with vsync off, the next frame is started sooner.
However, this does come at the expense of tearing, and at 240fps, I just don't think it's worth it. The amount of latency saved is fractions of a millisecond. Given even F1 drivers reaction times are in the order of 200 milliseconds, a fraction of a millisecond of saved latency is just pointless given it looks worse.
Also worth mentioning is that if a game has Nvidia reflex enabled and you turn on vsync it will be capped under the Hz limit to prevent input lag. So for me at 120 Hz games get capped at 116

