[Quang]

7w8: More self-identified with the need for adventure and lighter feelings. More playful and light. Expansive presence.
8w7: More self-identified with the need for independence and darker feelings. More charismatic and solid. Indomitable presence.

8s seek freedom for the sake of power and independence
7s seek power for the sake of freedom and stimulation

I suggest you also look for your instinctual subtype.

 

[Quang]

Don't know why they are thought to be so similar. Granted there are common attributes between them, yet let's not forget that 7s are an intellectual type, that is focused on how finely tuned their own perceptions are, and also what their connection to the "flow" of life is. 8 is about self-expression, pure, raw expansive freedom and the resistance against pressure from the outside world, as it's a type which focuses more on willpower.

They are two types that are often confused, especially when either of them have a strong wing supporting one another. Both have strong impulses, the need for excess, focus on the external, and are dynamic ID types, which can contribute to mistypings. 8s have more grounded solidity and presence than 7's scattered fluidity (flying/ slippery feel). I think how the types are connected contributes to why learning the enneagram is so interesting