That's a lot of arguments. Let me sort out where I stand on this vertical fist thing, and see if it helps.
To the best of my knowledge, you see a vertical fist in some Karate styles, in some Kung Fu styles (if you've seen chain punching, you know what I mean) and in JKD which is also known as Jun Fan Gong Fu, which is Bruce Lee's Chinese name. There are also some Savate strikes using a vertical fist.
The wraps and gloves that boxers use are intended primarily to protect their hands, not their opponent's face or body. Hitting your opponent for 12 rounds would risk terrible injury to your hands, and would profoundly shorten your career as a boxer.
My (4 years) background is in Muay Thai, so I've never done any other punching other than the conventional way, except for the short hook, as mentioned by Sensei up-thread. But I'm pretty sure that wraps and gloves would protect you no matter which way you hold your hands.
I don't know if your metacarpals are more or less prone to injury with horizontal or vertical punching with or without wraps and gloves. I would like to know.
The punching mechanics with vertical fists may be equal or superior for some strikes. I know the JKD guys do a chun-choi pak-sao hand trap into snappy punch that makes my face hurt. I can't say that its definitively better, but I don't discount stuff that Bruce Lee did without a good reason. Still, if you've ever seen Ali knock a guy out while moving backwards, you don't question that the conventional hand position can deliver a lot of power as well
The one area where I would definitely want a conventional hand position is with an uppercut or what I was taught is called a 'shovel-hook'. If you can throw a lead uppercut with a vertical fist that works as well as a horizontal one, you have my respect. I don't think it can be done.
As for advantages in any environment where you could end up on the ground, I think what you had for lunch that day will have more effect on your success than if you punch with your fist vertically or horizontally. The UFC guys wear those little 4 or 6 ounce gloves, with the fingers free so they can grapple, but they punch mostly with horizontal fists.