I did the external enclosure as Adam describes for my small 160GB drive. Good solution. I bought a $130 500 GB Seagate drive for my wife. Also a good solution.
You should take note of whether you're getting a true Terabyte drive or a 1TB drive composed of two 500 GB drives. Everything else being equal, there would be a (marginally?) higher risk of drive failure with 2x500 GB solution than a single 1x1000 GB solution.
In my meager opinion, all hard drives are equal. I'd prefer Seagate to Western Digital, as Seagate has a better reputation, but these are commodity devices now.
As for OWC -- as they're certainly buying their drives from the major manufacturers (WD, Seagate, etc.), what makes their products such better quality?