Well, I don't take notes of the exact model numbers that I've played with and such, but I'm pretty certain I've come across that one a few times by now... or at the very least one extremely similar. I've probably modded over 100 wii's for people (no exaggeration there) and I always tell them to buy WD drives.
And come to think of it, that one time that I had an issue with removing the preinstalled shitware could have possibly been a seagate drive because it is rare that someone can't find a WD drive at best buy or walmart, but it does happen.
About people telling you to worry about the auto sleep function, that was fixed all the way back at like cIOS v9 or earlier. Spanky Wanky (waninkoko) had put in code that would make the cIOS try to read the drive every couple of seconds to prevent the drives from going to sleep due to inactivity.
Trust me, you'll be fine.
And I personally prefer a portable drive because it is only powered by USB, so that means less wires and less electrical sockets being taken up. And for whoever said that the portables may perform slower... I say so me proof of it, and show me that it is a difference that is big enough to warrant that being a deciding factor. No matter what USB loading is WAY faster than loading from a retail disc, and from just my experience with computers and hard drives I think that the portable drives would be faster, especially since that have a faster spin up time.
No matter what, the hard drives themselves are capable of transfering data at much higher speeds, but the drive's bandwidth becomes limited by the USB interface. Just take a glance at SATA2 speeds verses USB2 speeds. I don't even think that USB2 can fully saturate a SATA1 drives interface.... but that I may be wrong about... but I doubt it. I'd have to look at the specs to know for sure... but it doesn't matter anyways.