Hello E.,
Both versions sound fine to me.
The version with "won't" relates to a current situation. For example, perhaps yesterday, they asked you to come to an event today. You are at the event; but they don't need your help. You are wondering why they asked you to come to the event, since they clearly won't need your help.
The version with "would" could relate to the same situation, or to a situation in the past.
Thus with the first version, it's clear that the situation is still current; but the second version is ambiguous, in that respect.
Best wishes,
MrP