Did you even read what you typed?
Lmfao, 5'3" 125 vs 6'4" 220 is the exact same thing as crocop vs hong man choi. You cannot be serious. (1)
If you have any training whatsoever, you'd understand the difference in skill. MM will destroy the middleweight champ of (insert name here championship). That is a fact. There's just no avoiding it. That .001 difference in timing is the making or breaking of a KO or sub. While mr. bigman is halfway to MMs face, MM is landing flush. Or landing a takedown. And before you know it, his small ass is throwing in that armbar. If you're an average guy, you stand NO chance.
The cardio of an average guy? The hell are you talking about? What is this mystical cardio of the average joe you speak of where the fight would need to be 30 min for MM to have an advantage??
An average guy that doesn't even smoke or drink or eat poorly can't jog for a minute or two without getting winded and having to stop.
Add in the fact that the average Joe smokes, drinks, and inhales oreos - he is completely fucked.
Add in the fact that you're getting elbowed in the face and might get ktfo or lose a joint, your shitty cardio just got worse. (2)
There are advantages and disadvantages for everything. Having a lot of size on someone also has huge disadvantages. People in this thread keep trying to say PHYSICS, PHYSICS. K, here's some physics for you. If you have a 5 foot piece of wood, then a 2 foot piece of wood, which ones is easier to kick through? Tall people are susceptible to having their knees blown out with a couple of flush power kicks. If you have that same board between your legs yanking on it, which one is easier to snap? Tall people have no leverage to combat a well executed submission. If you have 2 heavy barrels, and one has handles at the lower end and one has them at the higher end, which one is easier to lift off of the ground? It is much easier for a short guy to get in a tall guys crotch and take him down than the reverse. Tall guys have the reach to keep you at bay, but if you can get inside, their strikes have no leverage as the point of greatest impact will either be too short or too far, but the shorter guy has all the leverage and prime power stroke on the inside. The list goes on and on. The advantages of being taller are clear, but so are the disadvantages. (3)
Sign up for a legit gym and lay off the bong partner.