As above the AGU head has a greater peak flow. The best head depends what your looking to build the engine for.
In short gas velocity is as important a factor as peak gas flow and they are relative; for a given gas flow they are inversely proportional. These will certainly affect the cylinder fill capability and the way power is made.
The point where a large port head becomes more favourable depends on a number of factors, crucially this includes things such as what size turbo your looking to run; whether this will remain within the optimal compressor map for the given turbo, timing, power delivery and power itself.
Just depends what it is you want the car built for?
