Very good is two times above than above average imo. Good and than Very good.
Hmm. Interesting. Since we're talking hypothetical characters I'm going to use the Dungeons & Dragons character attribute system to answer this question. A notional fighter's performance in the cage would be determined primarily by his Strength, Dexterity and Constitution attributes. If he is an excellent trash talker with high Charisma, he has a chance to get inside his opponent's head but this effect should be relatively minor, perhaps imparting a +1 to initiative if anything.
So "master" rating would signify an 18 in that attribute, imparting a +3. If assigned to Strength, that fighter would receive +3 bonus to THACO as well as damage to melee strikes. Dexterity bonus would improve their Armor Class making them harder to hit and Constitution bonus would impart additional hit points per level. Since this is unarmed combat, weapon mastery is not a factor and we will presume none of the combatants are of the Mystic class.
And regardless of each combatant's fighting style, Wrestling Rating will factor heavily, which is the sum of Strength and Dexterity bonuses if any, plus proficiency bonus if trained in athletics or acrobatics.
Merely "Above Average" would signify an ability score between 13 and 15, imparting a +1 bonus, while "Very Good" signifies 16-17 and meriting +2 bonus.
So the match up can be quantified. Total attribute bonus for master with two above average attributes is +5. For Strength, Dexterity and Constitution all "above average" for +2 bonus each, imparts total +6 bonus across all physical attributes. Charisma-driven trash talk impact may move the needle but for simplicity we will presume that is a wash. So ceteris paribus, I believe a notional fighter with 16 scores across all physical abilities would likely be favored in unarmed melee combat over the other. However, a Monte Carlo simulation may be required.
