If the returns have refunds I would wait and efile in January. I think that will be quicker than snail mail.
But if money is owed i would mail the return to stop penalty and interest accruals.
I'm not sure if the IRS has announced the upcoming date officially, but for the last few years the first day of efiling for personal returns has been on or around January 27. The first day for business returns is around the 2nd week of January. At this point, you're probably right on the fence as to whether it would be better to mail the returns or wait for the new efiling season.