I think this debate on efficiency of EI vs torroid should be laid to rest since most psu designs involving EI and torroid trannies are overrated. Well at least to the DIY'er that is, say we need a max of 300VA, most DIY'ers use 600VA or even higher, talk about efficiency. 
There's really no debate at all as far as performance efficiency is concerned. The toroid wins hands down. But like I said efficiency has nothing to do with sonic qualities. The debate that I almost always encounter in many forums is on the claim that toroids impart better sonic qualities. That's where arguments from either side start to fly. And while I am on the camp that agrees with such a claim, I have no inclination to go into it.
And yes, in this hobby, it's always better to err on the side of plently. In my DIY years, I also would use over-rated transformers, electing to get a 1kva tranny when the specs required only 750va or thereabouts. Most of the time, I just get ready-made trannies from Raon and in the absence of a VA value I needed, I go for the next higher one.
And they were all EIs, though I would have loved getting a toroid if it were locally available at that time.
But in the area of production for business and commercie, that's not very prudent. You always talk about optimizing and getting just the right material quantity and quality for the job. Toroids fulfill not only a technical need but it dovetails nicely where efficiencies of operation are required.
