Superleo ,
Not sure if there is much scientific evidence regarding keeping them together, but just experience.
Your Leo's will be more stressed by keeping them together, this has been shown by owners who have had Geckos' together, then put them in seperate enclosures and they have flourished.
Also been shown by Gecko's living together OK and the next day they suddenly fight and one of them is badly hurt, if they enjoyed living together, why fight to the point of badly hurting one another.
They will always compete for food, hides and territory, usually the bigger one will always get more food, more territory and better hiding places, this will stress the smaller one a lot and make the smaller one at higher risk of illness because their immune system will be weaker.
They only sleep in the same hides due to instinct and also because they are competing for a certain hide.