Digital sales are more profitable for Nintendo, but the prices aren't very attractive. I pre-ordered Tropical Freeze for less than 33 Euros and it's at 49.99 in the eShop.
By the way: the speed of the internal flash memory is pretty slow, even external USB drives load the games faster.
My ZombiU (bought it a second time on the eShop for 9.99) measurements:
- Disk: 01:51.5.
- internal: 01:41.0
- external HDD: 01:37.5
- external SSD: 01:33.0
Method: I measured the time between clicking on the icon on the Wii U menu and the moment when the name of the survivor appears. I always measured it twice and Tte numbers are rounded mean valiues.
The internal memory and external SSD are loading the higher quality textures immediately. You can sometimes see very low-res textures for around 1 second with the Disk or external HDD.
The controls are also more responsive from internal or external memory. The Disk is struggling to load the data fast enough, it clatters all the time (this is not the case with Nintendo games).
