I don't see how it matters.
I would argue that ECML electrification has been more succesful, it is probably far better value for money than the Mark 1 equipment was.
Why are people these days so obsessed with gold plating everything?
While I'd agree that a balance needs to be struck, there are many reasons why you should avoid cost-cutting. Partly, it's a false economy, unless you are absolutely certain you can make it work, first time and every time. Otherwise, fixing the problems will wipe out all the savings. You can go too far either way (decorating the bridge abutments on the Invergarry and Fort Augustus being thoroughly gold-plated, the ECML wire problems being penny-pinched).
Also, the earlier equipment is
earlier. It was cutting-edge in its day, high-voltage a.c. was rare back then, so they may well have over-engineered some parts just to make sure that they worked. Work they did, although there were plenty of problems including the notorious transformer explosions and rectifier failures. Still, it was new and experimental then. The newer equipment was put up at a time when people knew it would work. However, they were probably a bit over-confident that their cost-savings would not make too much difference, plus pressure from the top. Hopefully, a compromise will be found.