Best for what? Mobile/portable storage containers are really nothing more than oversized boxes. Some are stripped down versions with nothing inside to tie-off with, are poorly ventilated, and have no moisture barriers. They are OK for local moves that can be accomplished on a single sunny day.
Most of the major vendors ( PODS, GoMini, SAM, Door-to-Door, etc) offer differing sizes that range from 7' to 16' in length. Properly packed, most of the larger units could probably accommodate a moderatley furnished two bedroom apartment.
The better question to ask, however, is whether or not the units can be dropped at each of the locations where you're moving. More and more communities have regulations restricting access of unmanned container units on public access thoroughfares and private property.
If you're moving interstate, compare prices for the type of service you're considering vs that of a full service mover. You really don't save much money by doing all of the work and assuming all of the liability and risk yourself.