Over at AA there was a long discussion on the merits of low DSR chokes, that moved on to power transformers. At first I thought the thread had promise. Well silly me.
Also it has been very hot here and with little or no AC. Perhaps I am a bit cranky.(No miserable little smile face)

So. After your very considered reply, I reread the thread. To go back to your original question, low verses high DSR. I can not think of a reason that you would want a high DSR secondary in a SE amp.

Does this mean that that the transformer with the lowest possible DSR is always the best? Good question. I have not looked at it in those terms,

Two points. First, remember, a transformer can be drawn ‘as a black box that is full of compromises’ (I rather like that one;)
Second, if you go and order ten different EI transformers with the same spec. you will end up with a collection that weighs in at say, 5lb to maybe 12lb or more and cost < $50 to maybe several hundred. Can the "goodness" be measured in DSR alone? Probably not but it may well be an indicator. Make a good green belt project for someone. .

There is much more to say on this. Such as OK John get to the point and how do you choose a power transformer.(Hint I look in my junk box first).But it still much too hot and I am starting to fade away. More later…John