Well, since the event you'd be going to will NOT actually have an effect on whether the nation rises or falls, or slavery remains or is abolished, and thus the "Confederate" side isn't a morally bankrupt bunch of racist bastards...
Talk to the people running it, and see which side treats you better. Who knows, maybe, in this case, the Southerners will actually treat you to some "Southern hospitality." It does exist, despite the best efforts of Southern Republicans to keep the stereotype of ignorance and bigotry going.