What's the recommended batch size?
Our answer: 4000
Unfortunately, there is no answer that fit all scenario. So there is no perfect answer to this question.
There are only two rules to follow:
There is so much thing that can impact the recommended batch size:
It doesn't worth it. SqlBulkCopy is already VERY fast and losing time to trying to improve will only get you a small gain of 10%? Which you may loose in some other case when some case has less or more row to insert.
The best recommendation you can get is to choose a value within your company and stick with it. Your time will be better invested elsewhere.
In this article, the XYZ recommended value without a doubt followed the "NOT too high, NOT too low" rule.
So yes, this is also an excellent recommended value!