Which is more standard, southerner English or northerner English?

Northerners, of course, because northerners speak Chinese closer to Mandarin. On the other hand, southerners usually can't pronounce the' er' sound or the retronasal sound correctly. In addition, southerners are educated and sometimes their teachers are not standard, especially in underdeveloped areas, so there must be something wrong with the pronunciation they teach. Maybe the grammatical angle between the north and the south is similar, but the pronunciation is definitely more correct for northerners.