It's much easier to close DCA early, since it closes early anyway.
DCA has far more space - surprised you'd think the DL party was more spread out since it's so much tighter quarters over there. The parade route at DCA is much longer, for instance, so it's easier to get a parade spot at DCA.
DL has the Haunted Mansion overlay, Halloween Screams fireworks, etc. (sometimes Ghost Galaxy), so it spreads the Halloween crowds out a bit more when that's all available for everyone.
I prefer the DCA party, myself.