I read quite a bit on Chowhound forum about Demet's and Verna's Donuts.
I made the trek to Demet's this morning. I have not tried Verna's yet.
I was very disappointed with Demet's. Not much jelly in the jelly donut and the honey dip was poor.
Imho, chowhound's should give DoughBoy Donuts a try. They are on Dorchester Ave across from the MBTA yards. They are heads above Demet's, for sure.
But, get there early, they sell out fast.