...it's a HUGE topic with lots of controversy. You must do the research yourself. Just remain skeptical...
I don't know what the OP's intent is for this thread, but what crebralfix said above is ultimately what any caliber discussion boils down to.
Most of what you read on forums and the like are people's opinion or preference which is all too often based on too little fact. And many will simply look for evidence that supports what they want to believe instead of searching for all information about the subject regardless of whether it supports or contradicts their opinion.
In my case, when I started getting interested in guns, I believed that the 9mm was the best round hands down. I liked it. It was the first caliber I shot with regularity. But I kept an open mind and asked questions and learned what was and wasn't good about the 9mm.
And I found my information not only on forums, but with those who have had far more experience with more calibers than I have (i.e. military personnel, law enforcement, firearm experts).
And what I have heard from them the most is: practice, comfort with a gun and caliber, knowledge of your firearm, and practice. The people I talk to often favor a caliber, but they always include that caveat.
I said that if I could have 5 rounds of any caliber and I didn't have to worry about going deaf or blind at night, I'd go with 44 magnum. Why did I say 44 magnum? Why not? I like the 44 because I can use it in a wheel gun and lever action. And because the OP's question is so open ended (no offense meant, just pointing out the obvious), I simply chose a practical round that has some added versatility.
Since choosing a caliber depends on so many things (gun type, person shooting the gun, intended use, cost, etc.), not having that information somewhat cripples the discussion.
