I choose...

A Professor of English is a more appropriate person to edit my writing than someone who left school at 15 with no qualifications,taking them both at face value. However some people who drop out of school go on to make a great success of themselves and may actually have excellent English. Hmmm...now I think about it, I think the current status and abilities of the native speaker should be compared to the current status and abilities of the Professor, rather than the achievement of a 15 year old with the achievement of an adult. That drop-out might now also be a Professor of English. We don't know.

...but assuming that the native still has the English of an unqualified 15 year old then, of course, the non-native Professor would be the better choice.

The fact that the native speaker is monolingual is not relevant though.

MrPedantic wrote:

Milky wrote: Who would you prefer to edit your writing: a non-native speaker of English who is a Professor of English at an Indian (or a Belgian) university, or a monolingual Brit or American who left school with no qualifications at the age of 15? I'm not sure we need to be quite as deferential towards professors of English as the question suggests. (Or quite as dismissive of monolingual 15-year-olds, for that matter.) MrP PS: Is the 15-year-old male or female, Milky?

Now, that would make a difference!!

<I think the current status and abilities of the native speaker should be compared to the current status and abilities of the Professor, rather than the achievement of a 15 year old with the achievement of an adult. That drop-out might now also be a Professor of English. We don't know.>

In my story, we do. He/she did not go on to higher education at all, found an ordinary job, but is a native speaker after all. So...