If you suddenly found out one day that one of your children had been switched at birth and that your son/daughter was not your actual blood son/daughter - would you love them any less? Would you be willing to let them go? Would you still die for them? I know I would - my kids are my life and it wouldn't matter to me if they were natural or not. My love for them has grown from my relationship with them - not from some biological similarity.
It's the same with adoption. Adopted children take hold in a parent's heart with the same strength and depth that a natural child does.
If it was all about biology then how could you explain natural parents that abuse their children? It's not about biology - it's about love.
So......with that in mind......choose the parents that you believe have the most love to give.