Just little sharing...
I also asked 蘇文峰 this question when he came to my home to check 'fung shui'.
As I planned to have BB in this year, I asked him whether 擇日生B was necessary, he said he didn't recommend wor... He also told me that there is 1/3 of chance that the date of birth affects a person's life, 1/3 affected by name, and another 1/3 affected by Fung Shui.