Flash Storage; External HD; WII U; little help SD gamers...?

Researching the subject of external memory storage for my kids’ WII U has yielded rather confusing results - I’m hoping for some clarification from those more expert in this area.

My kids got a copy of Xenoblade X for Christmas, and in reading about the game (on the Nintendo site, reviews on Amazon, comments on videos of gameplay posted online, etc.) there seems to be confusion/misinformation about using external storage for a game like this.

A few notes: I am in my early fifties, kids are in their low teens. I tend to be the one who is a bit more practically technically savvy (hooking stuff up, hardware, getting downloads to work, etc.) whereas they are more functionally proficient (as in, they kick my butt at just about any game they put their youthful little digits on) though I am finally getting good enough at Monster Hunter 4 to run with them. Finally.

So, my query:

Flash drives are suggested by some people as very good external storage for larger games like Xeno (first time any of us has tried a game quite like this - MH4U is next closest so far). Others absolutely trash the idea, citing that flashes have a limited lifespan, which I was unaware of until recently (well, every device has a finite life span, IMO, but I did not really understand what the limitations are on flashes, and have never had a problem with them under other uses).

Can anyone clarify this for me? If the issue is something like “can’t rewrite more than 100K times”, does that even matter from a practical gaming standpoint? I certainly don’t want to lose save data after getting deep into a complex game like this. I would cry. No, really. Cry.

Second, I have a nice 1TB external hard drive I could use, but it is USB powered, and Nintendo specifically notes on their site to use a self-powered HD for the WII U if you use one.

Is this really necessary? External HD’s don’t seem to use much power to run, and should get plenty from the USB connection, yes?

Finally, is external storage really needed at all? Gamers at message boards I looked through are all over the map on this point, as well as about the best type of storage. We haven’t used much of the WII’s own storage, but with 3 people playing a game like this, I imagine load times could bog down a bit…or a lot.

I turn to you, Dopers - best in the world at sorting out problems of this nature.

Your thoughts?
Thanks for any insight!

FWIW, specs on the above mentioned devices:

WD Elements external HD; 1 TB; USB 3.0

SanDisk 16 GB Flash Drive; USB 3.0; (up to) 245 MB/s read, 50 MB/s write

The Wii is only USB 2.0 though, I think, if that matters much.

Closed as a duplicate of a thread in GQ.