I had always believed that if you preserved a 16-bit workflow all the way up to the 8-bit print path, there would be very little (if any) benefit to sending and printing in 16-bit.
For general photographic output there is little if any difference assuming you are sending 16 bit images to the printer and allowing either Photoshop or Lightroom to handle the color transforms. When you do that and use the Adobe ACE CMM you are getting the advantage of 20 bits of precision in the working space to printer profile color transform. So, the difference between allowing Photoshop or Lightroom do the transform and printing 16 bit at the print head will be very slight.
Where 16 bit printing CAN help is when you apply long gentle gradations (like the Gradient Filter) on otherwise very smooth tones or colors. Also if you are outputting vector graphics from Illustrator or InDesign you can see a benefit to going the output in 16 bits.