What to consider when choosing between an internal or external hard drive?

Very simply, if you need it for storage, on a fixed PC, and are unlikely to need to use it outside your lan, go for an internal disk. If its gonna be going on walkabout, external disk. The internals are the same, but internal disks mostly use PATA or SATA, while external ones for most part use the slower USB interface, or ESATA, though the latter is not as common, and just sata.

"Store media mostly video : external.

Install games (or any other non-portable product) : only internal."