USB 2.0 has a overall throughput of ~35-40MB/s
the Wii U (in Wii U or WiiMode) cannot even read or write to it that fast.
using a SSD more expensive for higher capacity
uses less power, can be used without a Y cable if a 2.5in. no moving parts.
using a HDD not really expensive for a large capacity drive. will most likely need a Y cable if its a 2.5in. has moving parts
using a card reader:slower and expensive for larger capacity ones. Class 10 is only ~10MB/s
using a USB FlashDrive: Price in the middle of SSD and HDD. they are usually faster then SD cards. ~15-35MB/s depending on brand of FlashDrive used and its rated speed. More expensive then HDD for larger capacity.
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If you want the Wii U to be as portable as ever, get a FlashDrive, most are really small, and do not need more then 1 USB port. a good size one to get would be anywhere from 32 to 64GB , 64 if you plan to buy all games downloadable when possible vs a disk.
If you want the cheapest price per GB ratio, get a HDD, a 2.5in HDD is more portable then a 3.5in as you can use a Y cable vs a dedicated AC adapter. you can get a 500GB for around 60-80$, which is around what a 64GB flashdrive costs.
If you want a good compromise between the portability of a FlashDrive and the size of a HDD, get a SSD. ~120-140$ for a 128GB and ~200-240$ for a 256GB.
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I use a 250GB 5400RPM usb 2.5in hdd for mine. i use a Y cable to make sure it has enough power to run right.
for RPM's, A 5400RPM is good
7200 seems unnecessary for what the Wii U will use it for. and 10000 is downright overkill.
the Wii U will not noticeably benefit from faster RPM drives.
I use a 640GB 5400RPM in my Xbox360 (i have a jtag so is attached to it the same way a Microsoft Drive would, SATA)
load times are not a issue at all, using a 7200RPM may make a game load a second faster or 2 maybe but that's not enough to justify getting anything faster.
