From the NTP Pool Project (https://www.ntppool.org/en/use.html):
Looking up pool.ntp.org (or 0.pool.ntp.org, 1.pool.ntp.org, etc) will usually return IP addresses for servers in or close to your country. For most users this will give the best results.
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You can also use the continental zones (For example europe, north-america, oceania or asia.pool.ntp.org), and a country zone (like ch.pool.ntp.org in Switzerland) - for all these zones, you can again use the 0, 1 or 2 prefixes, like 0.ch.pool.ntp.org. Note, however, that the country zone might not exist for your country, or might contain only one or two timeservers.
I'm reading this several times and its not obvious whether I should specify the regional pool or not. I know which country my machine is in of course, so am happy to specify the pool. But it sounds like it doesn't result in better results.
Since the pool option means the protocol will select the best server after statistical analysis, I would have expected that specifying a regional pool would give a better distribution of servers from which to choose the winner. Any insights appreciated.