IMO, the advantage would be in the cold, if your hands are injured or you have large fingers. It was much easier handling the larger cases that's for sure. I have read though, where the 209 primers are actually too hot and "jump" the powder and projectile before the powder actually burns. That's why I bought the different breech plug. The 25 ACP, according to what I read, was just perfect for igniting the powder without the "jump".
Hmmm... Now you got me thinking again. Maybe I'll have to go back to the range and fool around with the breech plugs. I was using Pyrodex when I last tried the 25 ACP breech plug. Now I'm using 777. See what you started. :grin: