Usually, there are equal chances for anyone to get into a b-school in rounds 1 as well as 2. However, if you are planning to apply to US b-schools, they suggest you apply in round 1 itself because it takes time to get the VISA processing and other formalities done before you join the school, if and when you get admitted.
Most US b-schools have second round deadlines in January first or second week. So, assuming that you get your GMAT scores in the last week of December, you'll have very less time to prepare your essays and get your recommendations and other necessary stuff ready before the application deadlines - unless you've already taken care of these beforehand.
If you are targeting other non-US b-schools, for which you have sufficient time to prepare your application, then I would suggest you go ahead and apply this year. However, if it's the former case, then I would suggest you apply next year.
Check the post below for an exhaustive list of b-schools and their deadlines. Hope this helps!http://gmatclub.com/forum/all-mba-deadlines-massive-list-of-bschool-deadlines-121446.html
Hope to expect comments from other experts here
MBA Candidate 2015 | Georgetown University
McDonough School of Business