Is a bigger caliber rifle always better for hunting?

No. For instance a 300 Mag is great for larger game like Bear, Deer, Elk, Moose etc but would destroy a rabbit and on the other hand a plinker like a .22 lr is great for small game (yeas you can take large game with a well placed shot but that is a different issue and not legal) but you would not use it for larger game. I can't really tell people this enough if you want an all around weapon for hunting fowl, small game and most large game get a shotgun. Not only does a shotgun have a variety of shell types for different game you can also get a rifled slug barrel if you wanted to. You are sacrificing range but it does just about everything.

That's not a yes or no answer. It depends. If you are already using a caliber that is adequate for the game you are hunting then there is no point to using a bigger caliber. If you are hunting dangerous game then being a little overgunned might be a good thing.

A gun is just a tool. The whole reason for different calibers matching the right caliber to the job being done. That and people's inherent nature to try to make something better. Wildcatters have come up with some amazing cartridges over the years.

Nope. 22lr, 22wmr and 17hmr are excellent for small game that 270win, 30-06spfd and 308win would be ill suited for. Even in the same prey category, a caliber like 45-70govt is MUCH larger than 270win, yet at 300 yards the 270 is vastly superior due to its significantly flatter trajectory.

Shot placement is key. A 270 shot in the lungs is better than 50 bmg to the leg. Bigger cal for bigger animal is better too. For deer or cougar 243 min in my opinion and for elk or black bear 270 min

Always? No. You use what is comfortable for you to shoot accurately as long as it is legally and functionally capable of dropping the game with a single well placed shot. Keep in mind that the more powerful the gun, the more recoil and noise it produces. A good hunter practices and a gun that beats you to death is NOT something that you will want to devote the time to in order to become proficient.

No its not.

If you're hunting rabbit, upgrading from a .30-06 to a .50 BMG does not increase the amount of meat available for the stew pot.

I would say a larger caliber is rarely better for hunting.

Better to be slightly over caliber than slightly under. Dead animals hurt no one but wounded ones have been known for retaliation....severe injuries up to and including death.

It is not always better for hunting because it frightened the target very often because of its large size.