Post December interview question

I just received a post December interview and scheduled it for December 12th. My question is are post December interviews a lot more competitive to get an acceptance since half or more seats have been filled up? Also when would they let you know if you've been accepted because I have a few interviews that are pre-December and I don't want to reject them and gamble with my chances on an acceptance...
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums