99.9% of the time I think the high position is good on my Scania.
A handful of times over my nearly 9 year stint with this truck I have been approaching a roundabout and find that the right mirror has masked a vehicle from view necessitating a sharp stop when it suddenly comes into view when you are not expecting it.
It’s a pure chance thing, that the vehicle needs to be exactly masked in the exact time you look in that direction. The older 4 series I had never a top blind spot mirror on the offside so it was a shock when it happened first, subsequently I make sure I’m looking even more in such situations but it happened earlier in the week when a vehicle appeared out of nowhere. I assume they are hiding behind the mirrors 