Note that going to is often used for decisions made before speaking.
Will is often used for decisions made at the time of speaking.
Going to and will can both be used to make general predictions.
| If they win the election, | they'll raise taxes. |
| they're going to raise taxes. |
Only going to is generally used when there is present evidence.
Will can also be used to express:
-a request.
-an order.
-an invitation.
-a refusal.
-an offer.
-a promise.
-a threat.