Based on your experience, what is the more common 5.5mm power plug found on various wall warts - 2.1mm center or 2.5mm center? I'm designing a board that can take a wide range of voltage and I want to make it as generic as I can, with regard to warts the user may already have or warts we supply.
My sense is that 2.1mm is more common, but that's just one data point.