[Cathar]

Define what you want when you say "efficiency".

The PA radiators will achieve higher levels of overall heat dissipation performance than the HE radiators when using the exact same low-moderate throughput fans.

That basically means that the PA rads are more efficient in such scenarios.

Now when asking what is the most efficient fan to use, then really that is a question which cannot be answered. You need to specify a set goal, whether that be noise or cooling performance, or both, and then decide upon a suitable solution for those stated goals.

I think that this is perhaps what you're after when you say "efficient", but until you define what your goals are, the question can't be answered. You need to define what your needs are, and then construct a solution that suits. If you want high cooling performance for lower noise, than that is what the PA rads are very, very good at. As for an exact end-solution though, need to know what you want to achieve.