Saw the title and was hoping for pix :frown1:
Penis and ball size is more a result of evolution, i.e., inherited genes. During the time that testosterone is raging (in all but the few males with medical issues) and a male gains his permanent size, most guys will have a level that is high. Now, you will see some variation within families as posted elsewhere here but like most things gene related, size may skip a generation. Large cock and ball size is a result of nature needing to ensure procreation. Some men may need larger equipment in order to get the job done and/or become more attractive to potential mates (depending on what theory you buy into).
You will see an awful lot of tall, skinny guys with professions about as far away from the "macho" professioins, with the longest rods known to man.
re: horniness? It is just as much dependant upon the female hormone Estradiol in men as in women to achieve libido.
Edit: Oops, I see the OP has signed off and probably won't be back for another 10 months!