I think 8-12 weeks is better. At the shelter where I work we will NOT adopt out pups no later than 8-12 weeks to make sure they are healthy and everything.
Rescues or shelters who adopt out at 6 weeks, it's not good for the dogs plus it's irresponsible. And "breeders" who adopt out at 6 weeks especially BYBS it just seems if they sell them that young want their money faster.
A responsible breeder would sell the pups out at 8 weeks or more, but that's just me.
plus if they aren't fixed are only adding to the pet overpopulation problem because most of the time spay & neuter contracts do not get abided by at shelters and rescues.
We got Rudy at 6 weeks he was a rescue but we didn't intend to get him that young. This lady gave him to us (my family not the shelter) because her mom went to jail and the little kids weren't being friendly to him.
He has some aggression issues that we work on. He's 9 months old now. They younger they are IMO they are more prone to be aggressive later in life. No matter what, I think 8-12 weeks is ideal to stay with the mom even 8 weeks is good.
But if there's not a mom, there's nothing you can do about it if you have to bottle feed them.