Question about various rear ends

Hoping someone doesn't mind taking a quick minute to help educate me on something.

In doing research, it's become apparent to me that the 8 3/4 rear end with sure grip is the most desirable.....and some people even swear by the 8 1/4.

What I'm not clear on is the difference between the large bolt pattern and small bolt pattern. Why is the large bolt pattern preferred? Is the LBP only available on certain setups?

The other item that eludes me is the 3rd member variations. I keep reading about various numbers, but am not sure what the difference is and what is best suited for certain uses.

I currently have the dreaded 7 1/4 rear end and want to switch it out with something, but am trying to educate myself on what the various options are and what will work with various engine power/torque specs.

Also if there's some other tidbit of data that goes along with this topic that ties things together and I'm missing it, please let me know

Thanks guys.

Merry Christmas!

Mike