Pretty much what Stevensmay said. They're all pretty much the same honestly, it's a bit like paying attention to the brand of lightbulb or socks you have, they all tend to work the same. I suggest you stick to one of the two major manufacturers - Seagate or Western Digital but its not 100% necessary.
If i were you i'd be more concerned about the price and any extra features it has (ones that are real features too like USB3, not some made up stuff). I think 1TB should last you for ages, if its not too expensive, maybe upgrade to 2TB to future proof it. A downloaded movie is ~700mb or 0.7 GB, to make it simple (not technically correct though), a terabyte is 1000 Gigabytes. Say you have 100 downloaded movies that are 700mb each, thats only 70 gigabyte or 0.070 terabytes (out of 1) used so far. 5000 digital photos, assuming they're ~4mb each will roughly be 20 gigabyte or 0.020 terabytes.
As you can see its a serious amount of space. You might not even need that much, just see what the most cost effective option is.
Centrecom or MSY are usually very cheap for buying parts but they barely know the meaning of the word customer service. If you buy from them, know 100% what you want, they dont really like dealing with people who aren't sure but again, they are pretty damn cheap.