If you want to grow a Vidalia, or Texas 1015, or a Maui onion that taste exactly like a Vidalia, or Texas 1015, or Maui onion you would buy in the store ... you'll have to move to Vidalia, GA, the Rio Grande valley of Texas, or Maui.
The secret is the location ... the regional soil composition (low sulfur content is just one of the factors) and the climate (amount of sunlight and it's intensity, length of the days and nights, humidity, rainfall, temperatures both the daytime high and the nighttime lows, etc).
"It ain't what you don't know that gets you in trouble. It's what you know for sure that just ain't so." - Mark Twain