do you really not see the difference between the two?
No.
I don’t think considering the religious backgrounds of “Official Christian Holiday A” and “Official Christian Holiday B” has an effect in what way a Yid can participate or partake in either of them. Even in the context of giving gifts or sweets to those celebrating Holiday A or Holiday B.
The religious reasons the church established either of the two holidays should have no bearing on the limits of our commemorating or interacting with those holidays, however minor or major.
In short, there’s no halachic or hashkafic difference between giving Halloween candy to your neighbors for a Happy Halloween or giving Christmas presents to your neighbors for a Merry Christmas.