might as well vs. better off

[aaa]

Hi!
Could someone clear up for me difference in using "might as well"
and "better off", if any.

For instance, would there be any difference if I said "You'll be better
off if you play ball with him" instead of "You might as well play ball
with him" ?

[Tdol]

'You might as well' isn't the same, IMO; it means 'there's nothing to lose'. It's more negative- you might as well play with him- it probably won't benefit you much, or at all.

[aaa]

Can it mean that saying "I'm better off" I imply some benefit for myself, while saying "I might as well..." I imply some benefit for someone else?

[aaa]

up

[Tdol]

It could, or little if any benefit, but maybe worth a try (might as well).

[ruofei]

Can it mean that saying "I'm better off" I imply some benefit for myself, while saying "I might as well..." I imply some benefit for someone else?

This point interests me.
We can say that "I'm better off alone" and "I'd better be alone" are similar?

[Tdol]

I'd be better off alone = I don't need you
I'm better off alone = I work well alone, but might imply that I don't need assistance- it could be used professionally, but not when breaking with a partner, IMO.
I'd better be alone = could you go now (my partner's going to be back soon, for example)

[ruofei]

I'd be better off alone = I don't need you
I'm better off alone = I work well alone, but might imply that I don't need assistance- it could be used professionally, but not when breaking with a partner, IMO.
I'd better be alone = could you go now (my partner's going to be back soon, for example)

Thank you Tdol!

Just to make sure...
I'd [would (?)] be better off alone
I'd [had (?)] better be alone.

[Tdol]

I would be better off.
I had better be alone.

They're a bit unfair on learners.