I would make two comments about using 16bit printer. One is that once teaching a class, I printed a 4' by 17" print consisting of two white to black transitions as a demonstration of the difference of bit depth vs resolution. And a four foot 256 step grad right next to a four foot 65000 step grad is quite visibly astounding. This may not transfer into a real world advantage though, I am not sure.
The other point is that I tend to do a lot of photoshop work before I print and editing in 16bit files hardly ever get bashed very badly, as do the 8bit files. The histograms are usually smooth with no holes or spikes.
16bit files are a huge resource hog though. Some operations the take a few seconds in 8bit might take a minute or even more in 16bit. Saving the files is a pain also, although I have heard Adobe released a registry change that helps the files save, I believe, in 1/20 the time.
But as far as sending 8 or 16 bits to the printer, I am not sure I have noticed too much difference.