Metagame is an advantage play term that means “playing outside of game theory and mathematics”
A common question is
“why should I mug a bet when I can lay it at 0%”?
The short term (assessment of fair value aside), immediately selfish today’s bottom-line only answer is “there is no difference”. No metagame.
The metagame answer is “if everyone keeps on smashing that bet for way more than their bankroll should allow, like all those mumsnets with £30 on a 34/28 arb when they’d never dream of mugging £30 at 33/1 then this opportunity will never arise again”.
Perhaps you’re mugging a -EV Yankee to make your account look less like a value seeker because you hit £2k on a 2UP. Metagame.
Perhaps you’re taking a bet that is under the exchange price because you think the exchange price is wrong and you’re having the dual benefit of a perceived good price and also a < the exchange bet.