|3.5" hard drives are likely to last a lot longer than 2.5" hard drives. |
Some 3.5" hard drives have a 5 year warranty, e.g. most Seagate, some Western Digital models, some don't.
All 2.5" hard drives have a 3 year warranty.
Already assemled external drives may have only a one year warranty for the enclosure and the hard drive within it.
It's recommended you get an enclosure for 3.5" hard drives that has a fan or extra cooling .
An eSATA connected enclosure is better situation than a USB or firewire connected one - e.g. you will probably be able to transfer data faster with an eSATA connection than with the others - but if it needs to be usable with other computers, a USB one will work with any computer that has USB ports, IF the port is truly able to supply 500ma of current, AND the port is a type external drives can work with. See below.
The enclosure may or may not come with a USB or firewire or eSATA cable, but usually they do - that info is usually in the info about the product.
You don't need additional software, however, some enclosures come with a backup feature that may require you install software for that feature that is included or can be downloaded from the manufacturer's web site.
USB devices may not work correctly when they're connected to certain USB ports e.g. ports in a hub or on the front of a desktop case. If you have a desktop computer, you may have an IRQ sharing problem you need to fix, or your power supply may be starting to fail.
See response 3 in this:
Also - if you are using a USB extension cable, some of them have inadequate wiring and will not work properly with some USB devices.
External USB hard drive requirements.
See Response 9: