I've enjoyed a WD Black drive. Internal 4 GB is easy to find. I've owned one of those for almost 10 years no issues still runs just like new.
If you went with a NAS drive (WD Red) I'm not sure what the performance or other issues might be but, I would think you would want direct ethernet 1 gb connection for it or it would be as slow as downloading/uploading speeds over wi-fi.
The NAS drive ties into the modem directly and allows for all computers in the network to use it. I've never set one up before but I have considered it due to that feature. However, if all you want is local storage and large capacity skip the NAS and go to an internal or external large capacity HD.
External HD are nice, again you would want the fastest connection possible, also some of those come with their own power supply.