I posed a similar question to Roy Harrington... here's his reply:
Epson printers work at either 360 or 720. In the Epson driver "Finest Detail" selects 720ppi.
QTR driver always uses 720ppi. The Print-Tool program just sends the file as is to the OS.
It's the OS that will resample if needed to whatever the driver asks for.
So it can be worthwhile to send 720ppi to Print-Tool and QTR driver, but in general I think
just sending what you already have is just fine. (after all, resampling will happen anyway).