Actually, there is 4 types USB, EIDE, FIREWIRE, SCSI (maybe more, but I don't think so). These are the types of data transfer used. Most computers don't come with SCSI hardware. You would have to buy a SCSI card to control it, but it is slightly faster than IDE. Firewire is used mostly on MAC laptops, I think they can be used on PCs but I really don't know a lot about them. USB is the best if you want an external drive you can move from computer to computer, most newer computers today have USB ports on the back of your system already, it has the fastest data transfer rate, but I don't believe they make internal USB drives. The most typical kind is EIDE (IDE for short) which is most likely what your hard drive uses to communicate already and is already built into your motherboard if its a computer above a 386. This is the best choice for non-removable internal drives.
In short, go with USB for an external drive or IDE for an internal drive. SCSI and Firewire will require you buy extra controller cards to use them.