I can't tell who won the showboat contest.

Arm wrestling is about technique and leverage. Almost no strength involved.

Guy on the left has no leverage. Place about 2 inches under the right guy's elbow and Barbell Boy would spin him upside down.

The guy with the longer forearm loses.

I met an ex British arm-wrestling champion when i was on holiday in the south of France (he was sort of a holiday rep, but for a caravan park, and did more or less everything).

He was a big bloke, and said that muscle of course helps but that it was mostly down to technique. He didn't say anything about forearm length, but it stands to reason that the larger the angle between forearm and upper arm, the less 'turning' force you can produce.

Building up the bones and tendons through practice is pretty important as well, but yea, strength is definitely less important than most probably think. The main exception though i'd say is if you want to tricep press your opponent. You can hold someone much stronger than you with proper technique and enough endurance, but if you want to finish them with a tricep press you gotta have beastly triceps.

Muscle size is pretty much limited by bone strength. Thats why there is a limit and you can only go over it by using steroids. With bigger bones you also of course get stronger tendons.
And if you have a bad muscle to bone ratio, your bone snaps in an arm wrestling match.

Aye fair points, I guess what I'm sayin' though is that you don't necessarily need to aim for maximum muscle size in your workouts, you can perform exercises that stress your bones/tendons without really packing on much mass - i.e. static holds. Also, in terms of bones breaking, more muscle (compared to bone mass) will make it easier to break your arm, but usually it's always because of poor technique as well, i.e. putting yourself in the 'break arm' position. Pretty much exactly what happened to Nathan Jones in the WSM.

as soon as he 'broke' the guys wrist (bent it back), it was over... until then, he just needed to maintain the angle of the forearm to the upper arm while the other guy blew his load