It's essentially the difference between circuit switching (dedicating a whole physical link to a particular signal) and packet switching (breaking it down into

It's essentially the difference between circuit switching (dedicating a whole physical link to a particular signal) and packet switching (breaking it down into smaller chunks that can each be dealt with independently throughout a network, and then get reassembled on the other end). The former is easier to do (no overhead of disassembling/reassembling) but less flexible.