I'm not sure how good 8rack would be in legacy. Legacy decks are completely gross in their capabilities to win fast. gush plus fastbond puts so many cards in hand that it's ridiculous. 8rack could probably compete against creature decks like survival of the fittest, oath of druids,or hypergenesis but those combo decks with tendrils of agony are nuts.
Played both; Manaless is more consistent, as everything not required has been cut, but has a harder time games 2-3. LED has more explosive turns, but can sometimes just not work.
In terms of which is a better deck overall, LED dredge is the only one that places in SCG opens.
This isn't a very good indicator of which is a better deck. LED has much higher numbers of players taking it to an open. There are few who are willing to rock the manaless list through 8+ rounds.
Its the same with everything else, you don't want to give your opponent more information than you have to. The more threats/answers you can represent in hand, the less likely they are to play something they think will just get answered.
Manaless is more consistent simply because you have less chaff in the form of LED and draw-spells that you don't require. LED dredge runs half the creatures that manaless runs, making the ichorid plan less reliant than simply turning your deck over with lootings. Manaless can be more grindy where LED can just explode all over your opponent's face. Manaless can also go the entire game without casting any spells, reducing the interaction you receive from an opponent.
That's vintage you're thinking of.
This isn't a very good indicator of which is a better deck. LED has much higher numbers of players taking it to an open. There are few who are willing to rock the manaless list through 8+ rounds.