Thanks for your reply.
First, I have to file EAD for my wife since she cannot work without it.
Second, because I don't know whether I need EAD if i have to change my job since I cannot guarantee I will not lose my job and do the H1 transfer before I get my green card. I think that is why I need to get EAD for myself. Maybe I am wrong on this point.
Thanks and waiting for your further info.