You can fine tune a quad TB set-up a lot better with a lot of time and effort.
This is only going to smooth out the idle if the length of each runner prior to the TB (after the intake valve) has a larger volume than the cylinder it is filling.
I don't claim to be guru swami about this but it is definitely true on the NA engines that I have dealt with, and I would have to say that the same principle would apply at idle.