IMHO, i think that a decent Cubase - Logic Pro performance test may be blurred by the fact that Cubase uses VST and Logic uses Audio Units.
One should wonder if a VST and AU version of a plugin inherit differences in optimal code programming / performance.
If this is the case, than ofcourse the performance of both DAWs are influenced by the performance difference in plugin protocol they use.
Maybe this is just nonsense, then sorry, i am no expert in this area 
But i am very curious about what you have to say about this.
Best,
Robbie