Answer:
(it depends)
The original mix down format is the best place to start. However there are things to keep in mind. For many styles of music mixing to analog tape can be a wonderful thing. But sometimes it may not. Give yourself a backup plan and print identical mixes to at least a 24 bit digital format. Analog tape machines differ greatly in how worn out they may be, how customized they may be and the quality of the maintenance and alignment. Analog isn't a magical fix for just any recording. But in the well trained and practiced hands, mixing to analog can make a huge difference. One common misconception is "transferring digital mixes to analog makes the project sound more analog". I believe that this is only true about 10% of the time. When this question comes up for me, I make a VERY careful evaluation of the pros and cons of the analog transfer. It's often a difficult decision involving several compromises. So some patience and careful evaluation is needed here.
IF you mix back to your workstation try to use the highest quality A?D converter that you can afford. Like a good mic pre, it can make an enormous difference on you finished product. THIS IS IMPORTANT! Please do not "print" your mix with peak limiting. It will sound better; often MUCH better in the end to allow me to do my tone and level adjustments BEFORE the mix is peak limited. I'm not afraid of loud levels where it's called for and desired by the producer. But making tome changes (EQ) on a peak limited mix is always much less effective. Quite simply, the peak limiting really needs to be the very last process in the chain before making the final CD master.
