convince them? You should make a scandal and put the shop upside down if they do not change them! Besides, you can be clever and say that AFTER noticing all these problems you have investigated and discovered that a lot of people complain of the same, and so if they prefer to go for the standard legal way they would have to replace the same model three times before giving you the money back. At that point they will have lost THREE, not one headphone.
Which btw they do not loose anything because it is a complaint under warranty and they give it back to B&O.
And, you do not want money back, you want another headphone (which is even more expensive, I suppose).
Anyway yes, B&O have a good Customer Service. Despite the partial failure of the H8 they are still one of the best Audio Companies in the world. And everybody makes mistakes.
I have never said that. Comfort is a subjective thing. And they were not more comfortable to me, because I have small ears and the pads of the BBP are ok for me, and the BBP was more comfortable to me in the headband. But yeah, if your ears don't fit in the BBP and fit in the S1+ (which are not that much bigger) you may feel them more comfortable.
Hmmm, sorry, I do not wear glasses, but if I had to guess I would say that each option has pro and cons. The over ear would directly press on the arms of the glasses, the on ear would eventually/maybe press the ear which would/could press on the arms of the glasses.
I am afraid it is again a subjective thing and you would have to try yourself. Better would be not to send back the S1+ and order the BBP and compare the two and then decide which one to keep.
The head sensor is an advantage, definitely. Whatever may be the reason why you want to wear them off for a moment, you will be glad that the music stops.
Anyway you can disable this feature any time.
9% heavier, are you kidding?

If your head will notice it I would be surprised! But I admire your precision.
Smaller pads, as said, very relative thing. I never had a problem with them, nor many other people do.
I do indeed prefer large and deep earpads where my ears do not touch ANYTHING. But you do not find that often. And you, may not even want it or care about it.
S1+ better battery life? Do you really need more than 24 hrs in a row?
If I know my chickens I would guess you took your decision already and are not looking for suggestions but for permission.
I permit you to buy the BBP.