[Alright there's two main transmigration one being your soul is transferred from your body into and identical body and the bother being a different body.
Now transmigration into a identical body is the best choice due to being the safest option. Now hopefully your where death is imminent which will force you to be focused on survival and not be thinking about how your old life's is forever gone.
The second type is transmigrating into a different body like that Sasuke guy if who immediately died. This is the dangerous option where you have no idea the biology of your new body and think it's identical to your old one which it isn't. Let's talk about the most common transmigration the saiyan and you may be thinking what's wrong with that? Other then the pride, anger and other amplified emotions there's biological difference which you might abuse like a moron if zenkai boost was so powerful why don't all saiyans use it, simple answer zenkai boost uses life energy making your life span shorter for a power boost which is why many people die young as a saiyan because they don't understand biological differences and don't reseach about there biology like retards.
Now remember when transmigrating if you can make sure it's an identical body for maximum survivability.]