Did you say xxx is coming? I'm not coming.

"Did you say xxx is coming? I'm not coming."
1.The sentence far above is someone's remarks about party invitation. But why would this person said "I'm not coming." instead of "I'm not going to come (to your party)" or "I won't come to your party"? It seems like "I'm not coming." implies future, not ongoing situation. But this expression is foreign to me.

2.Is there any preference in English speakers when using the expression among "I'm not coming" "I'm not going to come" "I won't come"?

3. If that is not on the matters of preference, please explain to me the difference of ["Did you say xxx is coming?/I'm not coming"/"I'm not going to come"/"I won't come"]

Question

Did you say xxx is coming? I'm not coming.

"Did you say xxx is coming? I'm not coming."
1.The sentence far above is someone's remarks about party invitation. But why would this person said "I'm not coming." instead of "I'm not going to come (to your party)" or "I won't come to your party"? It seems like "I'm not coming." implies future, not ongoing situation. But this expression is foreign to me.

2.Is there any preference in English speakers when using the expression among "I'm not coming" "I'm not going to come" "I won't come"?

3. If that is not on the matters of preference, please explain to me the difference of ["Did you say xxx is coming?/I'm not coming"/"I'm not going to come"/"I won't come"]

Answer

1. Right, "I'm not coming" can indicate future activity. People say, for example, "my train is leaving tomorrow morning". The speaker is indicating an intent not to attend the future party.
2. All three are fairly harsh, not softened by any excuse, but "I'm not going to come" and "I won't come" seem more strident to me.
3. If any of the three can be said to be preferred, then best is "Did you say xxx is coming? I'm not coming".

Answer

There really is no difference in meaning, they all carry the same general idea that, the speaker of the sentence will not be at the party. It is just a style choice and more often then not, the 'laziness' in people bring out the shortest utterance that will take up the least amount of energy and time.

In this specific instance, politeness could be a factor which is why the speaker probably would not declare "I won't come" because it could be seen as rude.

Hope this helps,
Nick