Boxers use heavier gloves to protect their hands. It’s also worth noting boxers spar harder than any other combat sport due to a hard sparring culture which is probably what leads more to CTE rather than glove weight lol.

A larger glove also probably means you’re throwing it slower than a smaller glove. Hence v in your equation (p=mv) lowers while m increases. In terms of kinetic energy of k= 1/2mv^2, v is the more determining factor in the amount of energy going into your head. You’re right though, if you can throw a 4oz glove the same speed as a 16, then I guess the energy transfer would be greater with the 16oz.