IMO, the only meaningful difference between the Black and any other color is that the Black has a 5 year warranty. A 7200 RPM drive is going to perform like a 7200 RPM drive, regardless of color, cache, or other marketing. FWIW, cache size would matter for a boot drive, since the cache is designed to hold something that your HDD thinks you will need in the immediate future. It is unlikely that a storage drive would used in such a way that it would take advantage of that cache. If you are going to be loading a random 1GB movie from that HDD, it would not fit in cache anyway, and the HDD would not predict which one you wanted to access.
If you want something more reliable (in addition to the 5 year warranty), grab an RE (enterprise) drive. Each HDD brand has their own enterprise line, and they are an order of magnitude more reliable than the consumer options. Typically you pay at least 20% - 50% more than you would for a regular drive. If I recall, Toshiba's MG04, WD's RE, Seagate's Constellation, and HGST's Ultrastar are all enterprise lines.