Twice the chances of being detected
Double the attack surface
Half the performance
It really does not work like that. If you need a second adblocker to block somethings just enable the block list of the second one in the first one.
In fact just use uBlock Origin and be done with it.
I have only uBlock Origin and no YouTube update has gotten past it (except the first one for a few hours), I never get “disable adblocker” messages either. Also anti adblockers are not blacklist based.