3 end tanks 1 pipe and no extra merge points. 2 pipes add volume as well as surface area that will add to parasitic losses due to friction. Also by combining the 2 streams in 1 end tank you keep the turbulence that would otherwise be at the throttle body merge point all in the end tank where there is going to some any way. Volume is a huge concern in intercooling efficiency as per turbo response. The less volume the fill the less work it has to do and the faster the engine will come on boost.