Chris
What I think you are looking at is the output bit depth produced from the converted RAW file. If you are going to do any significant retouching then it may be advisable to keep the file initially as 16 bit then convert, if necessary to 8 bit.
16 bit file keep a lot more information when it comes to adjustment especially when density is concerned, however if you are using ACR then it will be making all it's adjustment in 16 bit, then outputting to 16 bit or 8 bit when it re renders the file to TIFF or JPEG.
If you are going to do any significant retouching in Photoshop, you may be better off keeping the image as 16 bit and convert to 8 bit if necessary for printing.
Remember 16 bit files can ens up being fairly big so that can slow things down on the computer
