I'd definitely go for option A. It makes it much easier to see that certain events happened close together, as can be seen from this example:
2020-12-20 02:45:30 GMT+8
2020-12-20 01:59:30 GMT+8
2020-12-20 01:59:26 GMT+8
2020-12-20 01:59:24 GMT+8
2020-12-20 01:59:20 GMT+8
2020-12-20 00:45:30 GMT+8
2020-12-20
02:45:30 GMT+8
2020-12-20
01:59:30 GMT+8
2020-12-20
01:59:26 GMT+8
2020-12-20
01:59:24 GMT+8
2020-12-20
01:59:20 GMT+8
2020-12-20
00:45:30 GMT+8
If you lack the horizontal space for this, consider dropping the timezone indication (but show it in the table footer), use a shorter date time format (e.g. "Dec 20, 01:59") or do use option B, but show the date only when it changes, e.g.
2020-12-21
08:15:10 GMT+8
2020-12-20
02:45:30 GMT+8
01:59:30 GMT+8
01:59:26 GMT+8
01:59:24 GMT+8
01:59:20 GMT+8
00:45:30 GMT+8
2020-12-19
16:15:10 GMT+8
The ability to quickly compare them matters less when showing only a single log, e.g. on a detail page or as a tooltip.