Are there any differences other than storabe size?1. Reliability.
2. Speed.
3. Noise.
4. RFI.
RE: (1). Hard to find a bulletproof drive. Judging from owner reports, some of the most reliable drives are made by Glyph. I own two of them and I'm very happy with them.
RE: (2) Speed is primarily determined by the connection between the drive and the computer. USB 3.0 and Firewire 800 are both sufficient for HD video, IME. Also, a solid state drive (SSD) will be more responsive than a hard disc drive (HDD), but also much more expensive.
RE: (3) Some drives have fans, some do not. Fans produce noise, which can be bothersome, depending on how loud the fan is and how far you sit from the drives. But fans keep heat down, and that improves reliability. The fans in the Glyph drives I linked above are fairly quiet.
RE: (4) A SSD will produce less RFI than a HDD. Whether that is audible is debatable, and probably system dependent. IME, SSD's can sound better than HDD's. Personally, I use a combination of drives. I have my better recordings on a SSD, and worse recordings on a HDD.
Hope that helps.
Bryon