Daryl-
Here is my 2 cents worth of personal advice after owning and shooting a 3" barreled 3" magnum Judge for a couple of years and maybe 400 total of all kinds of shells.
Take a look at the pellet load of a 2.5" or 3" .410 shotshell (you don't mention the cylinder length of what you are looking at) and you will find either 1/2 oz or what, 11/16 of an ounce of shot, say #6, perfect for normal rattlers or copperheads at your range of 5 yards. That load will contain somewhere around 120-150 or so pellets at .109".
Compare that with what you get with the factory loaded shot in .357,.45 or what have you, and you will find a huge difference in both weight of shot load and shot size.
I can assure you that The Judge is not easy to carry due to it's weight and size, but at reasonable range it is real serious Mojo for poisonous snakes. Only thing I can think of what would be more lethal would be a long barreled shotgun, which is even harder to carry, so go with The Judge if snake medicine is your main interest. It works fine.