So 23 milliseconds for the batch version and 850 milliseconds for RBAR. What a difference.
Now in this case the code for the RBAR is also a lot more complicated. But that isn’t always the case. It also isn’t always the case that RBAR is slower. But it’s almost always a lot slower than batch.
So, while the code for RBAR is often easier to write, even though it might be physically longer, it’s probably going to be slower too.
Well-written, set-based solutions aren’t always guaranteed to be faster, but that’s one of the safest bets to make with T-SQL.